- 04 Sep, 2015 40 commits
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Joseph Qi authored
There is a race case between crashed dio and rm, which will lead to OCFS2_VALID_FL not set read-only. N1 N2 ------------------------------------------------------------------------ dd with direct flag rm file crashed with an dio entry left in orphan dir clear OCFS2_VALID_FL in ocfs2_remove_inode recover N1 and read the corrupted inode, and set filesystem read-only So we skip the inode deletion this time and wait for dio entry recovered first. Signed-off-by:Joseph Qi <joseph.qi@huawei.com> Reviewed-by:
Mark Fasheh <mfasheh@suse.de> Cc: Joel Becker <jlbec@evilplan.org> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Yiwen Jiang authored
The following case will lead to a lockres is freed but is still in use. cat /sys/kernel/debug/o2dlm/locking_state dlm_thread lockres_seq_start -> lock dlm->track_lock -> get resA resA->refs decrease to 0, call dlm_lockres_release, and wait for "cat" unlock. Although resA->refs is already set to 0, increase resA->refs, and then unlock lock dlm->track_lock -> list_del_init() -> unlock -> free resA In such a race case, invalid address access may occurs. So we should delete list res->tracking before resA->refs decrease to 0. Signed-off-by:Yiwen Jiang <jiangyiwen@huawei.com> Reviewed-by:
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Tariq Saeed authored
This bug in mainline code is pointed out by Mark Fasheh. When ocfs2_iop_set_acl() and ocfs2_iop_get_acl() are entered from VFS layer, inode lock is not held. This seems to be regression from older kernels. The patch is to fix that. Orabug: 20189959 Signed-off-by:
Tariq Saeed <tariq.x.saeed@oracle.com> Reviewed-by:
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Tariq Saeed authored
PID: 614 TASK: ffff882a739da580 CPU: 3 COMMAND: "ocfs2dc" #0 [ffff882ecc3759b0] machine_kexec at ffffffff8103b35d #1 [ffff882ecc375a20] crash_kexec at ffffffff810b95b5 #2 [ffff882ecc375af0] oops_end at ffffffff815091d8 #3 [ffff882ecc375b20] die at ffffffff8101868b #4 [ffff882ecc375b50] do_trap at ffffffff81508bb0 #5 [ffff882ecc375ba0] do_invalid_op at ffffffff810165e5 #6 [ffff882ecc375c40] invalid_op at ffffffff815116fb [exception RIP: ocfs2_ci_checkpointed+208] RIP: ffffffffa0a7e940 RSP: ffff882ecc375cf0 RFLAGS: 00010002 RAX: 0000000000000001 RBX: 000000000000654b RCX: ffff8812dc83f1f8 RDX: 00000000000017d9 RSI: ffff8812dc83f1f8 RDI: ffffffffa0b2c318 RBP: ffff882ecc375d20 R8: ffff882ef6ecfa60 R9: ffff88301f272200 R10: 0000000000000000 R11: 0000000000000000 R12: ffffffffffffffff R13: ffff8812dc83f4f0 R14: 0000000000000000 R15: ffff8812dc83f1f8 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 #7 [ffff882ecc375d28] ocfs2_check_meta_downconvert at ffffffffa0a7edbd [ocfs2] #8 [ffff882ecc375d38] ocfs2_unblock_lock at ffffffffa0a84af8 [ocfs2] #9 [ffff882ecc375dc8] ocfs2_process_blocked_lock at ffffffffa0a85285 [ocfs2] #10 [ffff882ecc375e18] ocfs2_downconvert_thread_do_work at ffffffffa0a85445 [ocfs2] #11 [ffff882ecc375e68] ocfs2_downconvert_thread at ffffffffa0a854de [ocfs2] #12 [ffff882ecc375ee8] kthread at ffffffff81090da7 #13 [ffff882ecc375f48] kernel_thread_helper at ffffffff81511884 assert is tripped because the tran is not checkpointed and the lock level is PR. Some time ago, chmod command had been executed. As result, the following call chain left the inode cluster lock in PR state, latter on causing the assert. system_call_fastpath -> my_chmod -> sys_chmod -> sys_fchmodat -> notify_change -> ocfs2_setattr -> posix_acl_chmod -> ocfs2_iop_set_acl -> ocfs2_set_acl -> ocfs2_acl_set_mode Here is how. 1119 int ocfs2_setattr(struct dentry *dentry, struct iattr *attr) 1120 { 1247 ocfs2_inode_unlock(inode, 1); <<< WRONG thing to do. .. 1258 if (!status && attr->ia_valid & ATTR_MODE) { 1259 status = posix_acl_chmod(inode, inode->i_mode); 519 posix_acl_chmod(struct inode *inode, umode_t mode) 520 { .. 539 ret = inode->i_op->set_acl(inode, acl, ACL_TYPE_ACCESS); 287 int ocfs2_iop_set_acl(struct inode *inode, struct posix_acl *acl, ... 288 { 289 return ocfs2_set_acl(NULL, inode, NULL, type, acl, NULL, NULL); 224 int ocfs2_set_acl(handle_t *handle, 225 struct inode *inode, ... 231 { .. 252 ret = ocfs2_acl_set_mode(inode, di_bh, 253 handle, mode); 168 static int ocfs2_acl_set_mode(struct inode *inode, struct buffer_head ... 170 { 183 if (handle == NULL) { >>> BUG: inode lock not held in ex at this point <<< 184 handle = ocfs2_start_trans(OCFS2_SB(inode->i_sb), 185 OCFS2_INODE_UPDATE_CREDITS); ocfs2_setattr.#1247 we unlock and at #1259 call posix_acl_chmod. When we reach ocfs2_acl_set_mode.#181 and do trans, the inode cluster lock is not held in EX mode (it should be). How this could have happended? We are the lock master, were holding lock EX and have released it in ocfs2_setattr.#1247. Note that there are no holders of this lock at this point. Another node needs the lock in PR, and we downconvert from EX to PR. So the inode lock is PR when do the trans in ocfs2_acl_set_mode.#184. The trans stays in core (not flushed to disc). Now another node want the lock in EX, downconvert thread gets kicked (the one that tripped assert abovt), finds an unflushed trans but the lock is not EX (it is PR). If the lock was at EX, it would have flushed the trans ocfs2_ci_checkpointed -> ocfs2_start_checkpoint before downconverting (to NULL) for the request. ocfs2_setattr must not drop inode lock ex in this code path. If it does, takes it again before the trans, say in ocfs2_set_acl, another cluster node can get in between, execute another setattr, overwriting the one in progress on this node, resulting in a mode acl size combo that is a mix of the two. Orabug: 20189959 Signed-off-by: -
Norton.Zhu authored
Currently error handling in dlm_request_join is a little obscure, so optimize it to promote readability. If packet.code is invalid, reset it to JOIN_DISALLOW to keep it meaningful. It only influences the log printing. Signed-off-by:
Norton.Zhu <norton.zhu@huawei.com> Cc: Srinivas Eeda <srinivas.eeda@oracle.com> Reviewed-by:
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Yiwen Jiang authored
When running dirop_fileop_racer we found a case that inode can not removed. Two nodes, say Node A and Node B, mount the same ocfs2 volume. Create two dirs /race/1/ and /race/2/ in the filesystem. Node A Node B rm -r /race/2/ mv /race/1/ /race/2/ call ocfs2_unlink(), get the EX mode of /race/2/ wait for B unlock /race/2/ decrease i_nlink of /race/2/ to 0, and add inode of /race/2/ into orphan dir, unlock /race/2/ got EX mode of /race/2/. because /race/1/ is dir, so inc i_nlink of /race/2/ and update into disk, unlock /race/2/ because i_nlink of /race/2/ is not zero, this inode will always remain in orphan dir This patch fixes this case by test whether i_nlink of new dir is zero. Signed-off-by: -
WeiWei Wang authored
In ocfs2, ip_alloc_sem is used to protect allocation changes on the node. In direct IO, we add ip_alloc_sem to protect date consistent between direct-io and ocfs2_truncate_file race (buffer io use ip_alloc_sem already). Although inode->i_mutex lock is used to avoid concurrency of above situation, i think ip_alloc_sem is still needed because protect allocation changes is significant. Other filesystem like ext4 also uses rw_semaphore to protect data consistent between get_block-vs-truncate race by other means, So ip_alloc_sem in ocfs2 direct io is needed. Signed-off-by:
Weiwei Wang <wangww631@huawei.com> Signed-off-by:
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Goldwyn Rodrigues authored
In case a validation fails, clear the rest of the buffers and return the error to the calling function. This also facilitates bubbling up the error originating from ocfs2_error to calling functions. Signed-off-by:
Goldwyn Rodrigues <rgoldwyn@suse.com> Reviewed-by:
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Goldwyn Rodrigues authored
Caveat: This may return -EROFS for a read case, which seems wrong. This is happening even without this patch series though. Should we convert EROFS to EIO? Signed-off-by:
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Goldwyn Rodrigues authored
OCFS2 is often used in high-availaibility systems. However, ocfs2 converts the filesystem to read-only at the drop of the hat. This may not be necessary, since turning the filesystem read-only would affect other running processes as well, decreasing availability. This attempt is to add errors=continue, which would return the EIO to the calling process and terminate furhter processing so that the filesystem is not corrupted further. However, the filesystem is not converted to read-only. As a future plan, I intend to create a small utility or extend fsck.ocfs2 to fix small errors such as in the inode. The input to the utility such as the inode can come from the kernel logs so we don't have to schedule a downtime for fixing small-enough errors. The patch changes the ocfs2_error to return an error. The error returned depends on the mount option set. If none is set, the default is to turn the filesystem read-only. Perhaps errors=continue is not the best option name. Historically it is used for making an attempt to progress in the current process itself. Should we call it errors=eio? or errors=killproc? Suggestions/Comments welcome. Sources are available at: https://github.com/goldwynr/linux/tree/error-contSigned-off-by:
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Xue jiufei authored
Disk inode deletion may be heavily delayed when one node unlink a file after the same dentry is freed on another node(say N1) because of memory shrink but inode is left in memory. This inode can only be freed while N1 doing the orphan scan work. However, N1 may skip orphan scan for several times because other nodes may do the work earlier. In our tests, it may take 1 hour on 4 nodes cluster and it hurts the user experience. So we think the inode should be freed after the data flushed to disk when i_count becomes zero to avoid such circumstances. Signed-off-by:
Joyce.xue <xuejiufei@huawei.com> Cc: Joel Becker <jlbec@evilplan.org> Reviewed-by:
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Sanidhya Kashyap authored
The trusted extended attributes are only visible to the process which hvae CAP_SYS_ADMIN capability but the check is missing in ocfs2 xattr_handler trusted list. The check is important because this will be used for implementing mechanisms in the userspace for which other ordinary processes should not have access to. Signed-off-by:
Sanidhya Kashyap <sanidhya.gatech@gmail.com> Reviewed-by:
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jiangyiwen authored
In ocfs2_rename, it will lead to an inode with two entried(old and new) if ocfs2_delete_entry(old) failed. Thus, filesystem will be inconsistent. The case is described below: ocfs2_rename -> ocfs2_start_trans -> ocfs2_add_entry(new) -> ocfs2_delete_entry(old) -> __ocfs2_journal_access *failed* because of -ENOMEM -> ocfs2_commit_trans So filesystem should be set to read-only at the moment. Signed-off-by: -
Joseph Qi authored
Use list_for_each_entry instead of list_for_each to simplify code. Signed-off-by:
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Joseph Qi authored
The last goto statement is unneeded, so remove it. Signed-off-by:
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Joseph Qi authored
In dlm_register_domain_handlers, if o2hb_register_callback fails, it will call dlm_unregister_domain_handlers to unregister. This will trigger the BUG_ON in o2hb_unregister_callback because hc_magic is 0. So we should call o2hb_setup_callback to initialize hc first. Signed-off-by:
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Joseph Qi authored
status is already initialized and it will only be 0 or negatives in the code flow. So remove the unneeded assignment after the lable 'local'. Signed-off-by:
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Joseph Qi authored
Unlocking order in ocfs2_unlink and ocfs2_rename mismatches the corresponding locking order, although it won't cause issues, adjust the code so that it looks more reasonable. Signed-off-by:
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Joseph Qi authored
Since commit 86b9c6f3 ("ocfs2: remove filesize checks for sync I/O journal commit") removes filesize checks for sync I/O journal commit, variables old_size and old_clusters are not actually used any more. So clean them up. Signed-off-by:
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Christophe JAILLET authored
'o2hb_map_slot_data' and 'o2hb_populate_slot_data' are called from only one place, in 'o2hb_region_dev_write'. Return value is checked and 'mlog_errno' is called to log a message if it is not 0. So there is no need to call 'mlog_errno' directly within these functions. This would result on logging the message twice. Signed-off-by:
Christophe JAILLET <christophe.jaillet@wanadoo.fr> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <jlbec@evilplan.org> Signed-off-by:
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Joseph Qi authored
When storage network is unstable, it may trigger the BUG in __ocfs2_journal_access because of buffer not uptodate. We can retry the write in this case or return error instead of BUG. Signed-off-by:
Zhangguanghui <zhang.guanghui@h3c.com> Tested-by:
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Joseph Qi authored
1) Take rw EX lock in case of append dio. 2) Explicitly treat the error code -EIOCBQUEUED as normal. 3) Set di_bh to NULL after brelse if it may be used again later. Signed-off-by:
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Joseph Qi authored
During direct io the inode will be added to orphan first and then deleted from orphan. There is a race window that the orphan entry will be deleted twice and thus trigger the BUG when validating OCFS2_DIO_ORPHANED_FL in ocfs2_del_inode_from_orphan. ocfs2_direct_IO_write ... ocfs2_add_inode_to_orphan >>>>>>>> race window. 1) another node may rm the file and then down, this node take care of orphan recovery and clear flag OCFS2_DIO_ORPHANED_FL. 2) since rw lock is unlocked, it may race with another orphan recovery and append dio. ocfs2_del_inode_from_orphan So take inode mutex lock when recovering orphans and make rw unlock at the end of aio write in case of append dio. Signed-off-by: -
Alexander Kuleshov authored
Replace ((x) >> PAGE_SHIFT) with the predefined PFN_DOWN macro. Signed-off-by:
Alexander Kuleshov <kuleshovmail@gmail.com> Acked-by:
Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by:
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SF Markus Elfring authored
iput() tests whether its argument is NULL and then returns immediately. Thus the test around the call is not needed. This issue was detected by using the Coccinelle software. Signed-off-by:
Markus Elfring <elfring@users.sourceforge.net> Cc: Julia Lawall <julia.lawall@lip6.fr> Reviewed-by:
Anton Altaparmakov <anton@tuxera.com> Signed-off-by:
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Zhao Lei authored
I wrote a small script to show word-pair from all linux spelling-typo commits, and get following result by sort | uniq -c: 181 occured -> occurred 78 transfered -> transferred 67 recieved -> received 65 dependant -> dependent 58 wether -> whether 56 accomodate -> accommodate 54 occured -> occurred 51 recieve -> receive 47 cant -> can't 40 sucessfully -> successfully ... Some of them are not in spelling.txt, this patch adds the most common word-pairs into spelling.txt. Signed-off-by:Zhao Lei <zhaolei@cn.fujitsu.com> Signed-off-by:
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Robert Jarzmik authored
Fix the stack decoder for the ARM architecture. An ARM stack is designed as : [ 81.547704] [<c023eb04>] (bucket_find_contain) from [<c023ec88>] (check_sync+0x40/0x4f8) [ 81.559668] [<c023ec88>] (check_sync) from [<c023f8c4>] (debug_dma_sync_sg_for_cpu+0x128/0x194) [ 81.571583] [<c023f8c4>] (debug_dma_sync_sg_for_cpu) from [<c0327dec>] (__videobuf_s The current script doesn't expect the symbols to be bound by parenthesis, and triggers the following errors : awk: cmd. line:1: error: Unmatched ( or \(: / (check_sync$/ [ 81.547704] (bucket_find_contain) from (check_sync+0x40/0x4f8) Fix it by chopping starting and ending parenthesis from the each symbol name. As a side note, this probably comes from the function dump_backtrace_entry(), which is implemented differently for each architecture. That makes a single decoding script a bit a challenge. Signed-off-by:
Robert Jarzmik <robert.jarzmik@free.fr> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Russell King <rmk+kernel@arm.linux.org.uk> Cc: Michal Marek <mmarek@suse.cz> Signed-off-by:
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Jean Delvare authored
If indent is not found, bail out immediately instead of spitting random shell script error messages. Signed-off-by:
Jean Delvare <jdelvare@suse.de> Cc: Joe Perches <joe@perches.com> Signed-off-by:
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Bart Van Assche authored
Editors like emacs and vi recognize a number of error message formats. The format used by the kerneldoc tool is not recognized by emacs. Change the kerneldoc error message format to the GNU style such that the emacs prev-error and next-error commands can be used to navigate through kerneldoc error messages. For more information about the GNU error message format, see also https://www.gnu.org/prep/standards/html_node/Errors.html. This patch has been generated via the following sed command: sed -i.orig 's/Error(\${file}:\$.):/\${file}:\$.: error:/g;s/Warning(\${file}:\$.):/\${file}:\$.: warning:/g;s/Warning(\${file}):/\${file}:1: warning:/g;s/Info(\${file}:\$.):/\${file}:\$.: info:/g' scripts/kernel-doc Signed-off-by:
Bart Van Assche <bart.vanassche@sandisk.com> Cc: Johannes Berg <johannes.berg@intel.com> Acked-by:
Randy Dunlap <rdunlap@infradead.org> Signed-off-by:
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Sudip Mukherjee authored
I just did a spelling mistake of uninitialized and wrote that as unintialized. Fortunately I noticed it in my final review. Signed-off-by:
Sudip Mukherjee <sudip@vectorindia.org> Signed-off-by:
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Maninder Singh authored
misspelled words for check:- chcek chck cehck I myself did these spell mistakes in changelog for patches, Thus suggesting to add in spelling.txt, so that checkpatch.pl warns it earlier. References:- ./arch/powerpc/kernel/exceptions-64e.S:456: . . . make sure you chcek https://lkml.org/lkml/2015/6/25/289 ./arch/x86/mm/pageattr.c:1368: * No need to cehck in that case [akpm@linux-foundation.org: add whcih->which, whcih I always get wrong] Signed-off-by:
Maninder Singh <maninder1.s@samsung.com> Acked-by:
Kees Cook <keescook@chromium.org> Signed-off-by:
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Jan Kara authored
fsnotify_destroy_mark_locked() is subtle to use because it temporarily releases group->mark_mutex. To avoid future problems with this function, split it into two. fsnotify_detach_mark() is the part that needs group->mark_mutex and fsnotify_free_mark() is the part that must be called outside of group->mark_mutex. This way it's much clearer what's going on and we also avoid some pointless acquisitions of group->mark_mutex. Signed-off-by:
Jan Kara <jack@suse.com> Signed-off-by:
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Jan Kara authored
Free list is used when all marks on given inode / mount should be destroyed when inode / mount is going away. However we can free all of the marks without using a special list with some care. Signed-off-by:
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Jan Kara authored
Signed-off-by:
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Jan Kara authored
A check in inotify_fdinfo() checking whether mark is valid was always true due to a bug. Luckily we can never get to invalidated marks since we hold mark_mutex and invalidated marks get removed from the group list when they are invalidated under that mutex. Anyway fix the check to make code more future proof. Signed-off-by:
Jan Kara <jack@suse.cz> Signed-off-by:
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Dave Hansen authored
I have a _tiny_ microbenchmark that sits in a loop and writes single bytes to a file. Writing one byte to a tmpfs file is around 2x slower than reading one byte from a file, which is a _bit_ more than I expecte. This is a dumb benchmark, but I think it's hard to deny that write() is a hot path and we should avoid unnecessary overhead there. I did a 'perf record' of 30-second samples of read and write. The top item in a diffprofile is srcu_read_lock() from fsnotify(). There are active inotify fd's from systemd, but nothing is actually listening to the file or its part of the filesystem. I *think* we can avoid taking the srcu_read_lock() for the common case where there are no actual marks on the file. This means that there will both be nothing to notify for *and* implies that there is no need for clearing the ignore mask. This patch gave a 13.1% speedup in writes/second on my test, which is an improvement from the 10.8% that I saw with the last version. Signed-off-by:
Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by:
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Yuriy Kolerov authored
Architectures which support VGA console must define screen_info structurture from "uapi/linux/screen_info.h". Otherwise undefined symbol error occurs. Usually it's defined in "setup.c" for each architecture. If an architecture does not support VGA console (ARC's case) there are 2 ways: define a dummy instance of screen_info or add a negative dependency for VGA_CONSOLE in to prevent selecting this option. I've implemented the second way. However the best solution is to add HAVE_VGA_CONSOLE option for targets which support VGA console. Then turn off VGA_CONSOLE by default and add dependency to HAVE_VGA_CONSOLE. But right now it's better to just add a negative dependency for ARC and then consider how to collaborate about this issue with maintainers of other architectures. Signed-off-by:
Yuriy Kolerov <yuriy.kolerov@synopsys.com> Acked-by:
Geert Uytterhoeven <geert@linux-m68k.org> Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com> Cc: Tomi Valkeinen <tomi.valkeinen@ti.com> Cc: Jaya Kumar <jayalk@intworks.biz> Cc: Vineet Gupta <vgupta@synopsys.com> Signed-off-by:
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Andy Lutomirski authored
Per Andrew Morgan's request, add a securebit to allow admins to disable PR_CAP_AMBIENT_RAISE. This securebit will prevent processes from adding capabilities to their ambient set. For simplicity, this disables PR_CAP_AMBIENT_RAISE entirely rather than just disabling setting previously cleared bits. Signed-off-by:
Andy Lutomirski <luto@kernel.org> Acked-by:
Andrew G. Morgan <morgan@kernel.org> Acked-by:
Serge Hallyn <serge.hallyn@canonical.com> Cc: Kees Cook <keescook@chromium.org> Cc: Christoph Lameter <cl@linux.com> Cc: Serge Hallyn <serge.hallyn@canonical.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Aaron Jones <aaronmdjones@gmail.com> Cc: Ted Ts'o <tytso@mit.edu> Cc: Andrew G. Morgan <morgan@kernel.org> Cc: Mimi Zohar <zohar@linux.vnet.ibm.com> Cc: Austin S Hemmelgarn <ahferroin7@gmail.com> Cc: Markku Savela <msa@moth.iki.fi> Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: James Morris <james.l.morris@oracle.com> Signed-off-by:
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Andy Lutomirski authored
This test focuses on ambient capabilities. It requires either root or the ability to create user namespaces. Some of the test cases will be skipped for nonroot users. Signed-off-by:
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Andy Lutomirski authored
Credit where credit is due: this idea comes from Christoph Lameter with a lot of valuable input from Serge Hallyn. This patch is heavily based on Christoph's patch. ===== The status quo ===== On Linux, there are a number of capabilities defined by the kernel. To perform various privileged tasks, processes can wield capabilities that they hold. Each task has four capability masks: effective (pE), permitted (pP), inheritable (pI), and a bounding set (X). When the kernel checks for a capability, it checks pE. The other capability masks serve to modify what capabilities can be in pE. Any task can remove capabilities from pE, pP, or pI at any time. If a task has a capability in pP, it can add that capability to pE and/or pI. If a task has CAP_SETPCAP, then it can add any capability to pI, and it can remove capabilities from X. Tasks are not the only things that can have capabilities; files can also have capabilities. A file can have no capabilty information at all [1]. If a file has capability information, then it has a permitted mask (fP) and an inheritable mask (fI) as well as a single effective bit (fE) [2]. File capabilities modify the capabilities of tasks that execve(2) them. A task that successfully calls execve has its capabilities modified for the file ultimately being excecuted (i.e. the binary itself if that binary is ELF or for the interpreter if the binary is a script.) [3] In the capability evolution rules, for each mask Z, pZ represents the old value and pZ' represents the new value. The rules are: pP' = (X & fP) | (pI & fI) pI' = pI pE' = (fE ? pP' : 0) X is unchanged For setuid binaries, fP, fI, and fE are modified by a moderately complicated set of rules that emulate POSIX behavior. Similarly, if euid == 0 or ruid == 0, then fP, fI, and fE are modified differently (primary, fP and fI usually end up being the full set). For nonroot users executing binaries with neither setuid nor file caps, fI and fP are empty and fE is false. As an extra complication, if you execute a process as nonroot and fE is set, then the "secure exec" rules are in effect: AT_SECURE gets set, LD_PRELOAD doesn't work, etc. This is rather messy. We've learned that making any changes is dangerous, though: if a new kernel version allows an unprivileged program to change its security state in a way that persists cross execution of a setuid program or a program with file caps, this persistent state is surprisingly likely to allow setuid or file-capped programs to be exploited for privilege escalation. ===== The problem ===== Capability inheritance is basically useless. If you aren't root and you execute an ordinary binary, fI is zero, so your capabilities have no effect whatsoever on pP'. This means that you can't usefully execute a helper process or a shell command with elevated capabilities if you aren't root. On current kernels, you can sort of work around this by setting fI to the full set for most or all non-setuid executable files. This causes pP' = pI for nonroot, and inheritance works. No one does this because it's a PITA and it isn't even supported on most filesystems. If you try this, you'll discover that every nonroot program ends up with secure exec rules, breaking many things. This is a problem that has bitten many people who have tried to use capabilities for anything useful. ===== The proposed change ===== This patch adds a fifth capability mask called the ambient mask (pA). pA does what most people expect pI to do. pA obeys the invariant that no bit can ever be set in pA if it is not set in both pP and pI. Dropping a bit from pP or pI drops that bit from pA. This ensures that existing programs that try to drop capabilities still do so, with a complication. Because capability inheritance is so broken, setting KEEPCAPS, using setresuid to switch to nonroot uids, and then calling execve effectively drops capabilities. Therefore, setresuid from root to nonroot conditionally clears pA unless SECBIT_NO_SETUID_FIXUP is set. Processes that don't like this can re-add bits to pA afterwards. The capability evolution rules are changed: pA' = (file caps or setuid or setgid ? 0 : pA) pP' = (X & fP) | (pI & fI) | pA' pI' = pI pE' = (fE ? pP' : pA') X is unchanged If you are nonroot but you have a capability, you can add it to pA. If you do so, your children get that capability in pA, pP, and pE. For example, you can set pA = CAP_NET_BIND_SERVICE, and your children can automatically bind low-numbered ports. Hallelujah! Unprivileged users can create user namespaces, map themselves to a nonzero uid, and create both privileged (relative to their namespace) and unprivileged process trees. This is currently more or less impossible. Hallelujah! You cannot use pA to try to subvert a setuid, setgid, or file-capped program: if you execute any such program, pA gets cleared and the resulting evolution rules are unchanged by this patch. Users with nonzero pA are unlikely to unintentionally leak that capability. If they run programs that try to drop privileges, dropping privileges will still work. It's worth noting that the degree of paranoia in this patch could possibly be reduced without causing serious problems. Specifically, if we allowed pA to persist across executing non-pA-aware setuid binaries and across setresuid, then, naively, the only capabilities that could leak as a result would be the capabilities in pA, and any attacker *already* has those capabilities. This would make me nervous, though -- setuid binaries that tried to privilege-separate might fail to do so, and putting CAP_DAC_READ_SEARCH or CAP_DAC_OVERRIDE into pA could have unexpected side effects. (Whether these unexpected side effects would be exploitable is an open question.) I've therefore taken the more paranoid route. We can revisit this later. An alternative would be to require PR_SET_NO_NEW_PRIVS before setting ambient capabilities. I think that this would be annoying and would make granting otherwise unprivileged users minor ambient capabilities (CAP_NET_BIND_SERVICE or CAP_NET_RAW for example) much less useful than it is with this patch. ===== Footnotes ===== [1] Files that are missing the "security.capability" xattr or that have unrecognized values for that xattr end up with has_cap set to false. The code that does that appears to be complicated for no good reason. [2] The libcap capability mask parsers and formatters are dangerously misleading and the documentation is flat-out wrong. fE is *not* a mask; it's a single bit. This has probably confused every single person who has tried to use file capabilities. [3] Linux very confusingly processes both the script and the interpreter if applicable, for reasons that elude me. The results from thinking about a script's file capabilities and/or setuid bits are mostly discarded. Preliminary userspace code is here, but it needs updating: https://git.kernel.org/cgit/linux/kernel/git/luto/util-linux-playground.git/commit/?h=cap_ambient&id=7f5afbd175d2 Here is a test program that can be used to verify the functionality (from Christoph): /* * Test program for the ambient capabilities. This program spawns a shell * that allows running processes with a defined set of capabilities. * * (C) 2015 Christoph Lameter <cl@linux.com> * Released under: GPL v3 or later. * * * Compile using: * * gcc -o ambient_test ambient_test.o -lcap-ng * * This program must have the following capabilities to run properly: * Permissions for CAP_NET_RAW, CAP_NET_ADMIN, CAP_SYS_NICE * * A command to equip the binary with the right caps is: * * setcap cap_net_raw,cap_net_admin,cap_sys_nice+p ambient_test * * * To get a shell with additional caps that can be inherited by other processes: * * ./ambient_test /bin/bash * * * Verifying that it works: * * From the bash spawed by ambient_test run * * cat /proc/$$/status * * and have a look at the capabilities. */ #include <stdlib.h> #include <stdio.h> #include <errno.h> #include <cap-ng.h> #include <sys/prctl.h> #include <linux/capability.h> /* * Definitions from the kernel header files. These are going to be removed * when the /usr/include files have these defined. */ #define PR_CAP_AMBIENT 47 #define PR_CAP_AMBIENT_IS_SET 1 #define PR_CAP_AMBIENT_RAISE 2 #define PR_CAP_AMBIENT_LOWER 3 #define PR_CAP_AMBIENT_CLEAR_ALL 4 static void set_ambient_cap(int cap) { int rc; capng_get_caps_process(); rc = capng_update(CAPNG_ADD, CAPNG_INHERITABLE, cap); if (rc) { printf("Cannot add inheritable cap\n"); exit(2); } capng_apply(CAPNG_SELECT_CAPS); /* Note the two 0s at the end. Kernel checks for these */ if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, cap, 0, 0)) { perror("Cannot set cap"); exit(1); } } int main(int argc, char **argv) { int rc; set_ambient_cap(CAP_NET_RAW); set_ambient_cap(CAP_NET_ADMIN); set_ambient_cap(CAP_SYS_NICE); printf("Ambient_test forking shell\n"); if (execv(argv[1], argv + 1)) perror("Cannot exec"); return 0; } Signed-off-by: Christoph Lameter <cl@linux.com> # Original author Signed-off-by:
Serge E. Hallyn <serge.hallyn@ubuntu.com> Acked-by:
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