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  1. 24 May, 2023 1 commit
    • David Sterba's avatar
      fs: use UB-safe check for signed addition overflow in remap_verify_area · b7a9a503
      David Sterba authored 
      The following warning pops up with enabled UBSAN in tests fstests/generic/303:

  [23127.529395] UBSAN: Undefined behaviour in fs/read_write.c:1725:7
  [23127.529400] signed integer overflow:
  [23127.529403] 4611686018427322368 + 9223372036854775807 cannot be represented in type 'long long int'
  [23127.529412] CPU: 4 PID: 26180 Comm: xfs_io Not tainted 5.2.0-rc2-1.ge195904-vanilla+ #450
  [23127.556999] Hardware name: empty empty/S3993, BIOS PAQEX0-3 02/24/2008
  [23127.557001] Call Trace:
  [23127.557060]  dump_stack+0x67/0x9b
  [23127.557070]  ubsan_epilogue+0x9/0x40
  [23127.573496]  handle_overflow+0xb3/0xc0
  [23127.573514]  do_clone_file_range+0x28f/0x2a0
  [23127.573547]  vfs_clone_file_range+0x35/0xb0
  [23127.573564]  ioctl_file_clone+0x8d/0xc0
  [23127.590144]  do_vfs_ioctl+0x300/0x700
  [23127.590160]  ksys_ioctl+0x70/0x80
  [23127.590203]  ? trace_hardirqs_off_thunk+0x1a/0x1c
  [23127.590210]  __x64_sys_ioctl+0x16/0x20
  [23127.590215]  do_syscall_64+0x5c/0x1d0
  [23127.590224]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
  [23127.590231] RIP: 0033:0x7ff6d7250327
  [23127.590241] RSP: 002b:00007ffe3a38f1d8 EFLAGS: 00000206 ORIG_RAX: 0000000000000010
  [23127.590246] RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007ff6d7250327
  [23127.590249] RDX: 00007ffe3a38f220 RSI: 000000004020940d RDI: 0000000000000003
  [23127.590252] RBP: 0000000000000000 R08: 00007ffe3a3c80a0 R09: 00007ffe3a3c8080
  [23127.590255] R10: 000000000fa99fa0 R11: 0000000000000206 R12: 0000000000000000
  [23127.590260] R13: 0000000000000000 R14: 3fffffffffff0000 R15: 00007ff6d750a20c

As loff_t is a signed type, we should use the safe overflow checks
instead of relying on compiler implementation.

The bogus values are intentional and the test is supposed to verify the
boundary conditions.
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
Message-Id: <20230523162628.17071-1-dsterba@suse.com>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      b7a9a503
  3. 17 May, 2023 4 commits
    • Arnd Bergmann's avatar
      procfs: consolidate arch_report_meminfo declaration · ef104443
      Arnd Bergmann authored 
      The arch_report_meminfo() function is provided by four architectures,
with a __weak fallback in procfs itself. On architectures that don't
have a custom version, the __weak version causes a warning because
of the missing prototype.

Remove the architecture specific prototypes and instead add one
in linux/proc_fs.h.
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com> # for arch/x86
Acked-by: Helge Deller <deller@gmx.de> # parisc
Reviewed-by: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
Message-Id: <20230516195834.551901-1-arnd@kernel.org>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      ef104443
    • Arnd Bergmann's avatar
      fs: pipe: reveal missing function protoypes · 247c8d2f
      Arnd Bergmann authored 
      A couple of functions from fs/pipe.c are used both internally
and for the watch queue code, but the declaration is only
visible when the latter is enabled:

fs/pipe.c:1254:5: error: no previous prototype for 'pipe_resize_ring'
fs/pipe.c:758:15: error: no previous prototype for 'account_pipe_buffers'
fs/pipe.c:764:6: error: no previous prototype for 'too_many_pipe_buffers_soft'
fs/pipe.c:771:6: error: no previous prototype for 'too_many_pipe_buffers_hard'
fs/pipe.c:777:6: error: no previous prototype for 'pipe_is_unprivileged_user'

Make the visible unconditionally to avoid these warnings.

Fixes: c73be61c ("pipe: Add general notification queue support")
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Message-Id: <20230516195629.551602-1-arnd@kernel.org>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      247c8d2f
    • Arnd Bergmann's avatar
      fs: d_path: include internal.h · df67cb4c
      Arnd Bergmann authored 
      make W=1 warns about a missing prototype that is defined but
not visible at point where simple_dname() is defined:

fs/d_path.c:317:7: error: no previous prototype for 'simple_dname' [-Werror=missing-prototypes]
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Message-Id: <20230516195444.551461-1-arnd@kernel.org>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      df67cb4c
    • Vladimir Sementsov-Ogievskiy's avatar
      coredump: require O_WRONLY instead of O_RDWR · 88e46070
      Vladimir Sementsov-Ogievskiy authored 
      The motivation for this patch has been to enable using a stricter
apparmor profile to prevent programs from reading any coredump in the
system.

However, this became something else. The following details are based on
Christian's and Linus' archeology into the history of the number "2" in
the coredump handling code.

To make sure we're not accidently introducing some subtle behavioral
change into the coredump code we set out on a voyage into the depths of
history.git to figure out why this was O_RDWR in the first place.

Coredump handling was introduced over 30 years ago in commit
ddc733f4 ("[PATCH] Linux-0.97 (August 1, 1992)").
The original code used O_WRONLY:

    open_namei("core",O_CREAT | O_WRONLY | O_TRUNC,0600,&inode,NULL)

However, this changed in 1993 and starting with commit
9cb9f18b ("[PATCH] Linux-0.99.10 (June 7, 1993)") the coredump code
suddenly used the constant "2":

    open_namei("core",O_CREAT | 2 | O_TRUNC,0600,&inode,NULL)

This was curious as in the same commit the kernel switched from
constants to proper defines in other places such as KERNEL_DS and
USER_DS and O_RDWR did already exist.

So why was "2" used? It turns out that open_namei() - an early version
of what later turned into filp_open() - didn't accept O_RDWR.

A semantic quirk of the open() uapi is the definition of the O_RDONLY
flag. It would seem natural to define:

    #define O_RDWR (O_RDONLY | O_WRONLY)

but that isn't possible because:

    #define O_RDONLY 0

This makes O_RDONLY effectively meaningless when passed to the kernel.
In other words, there has never been a way - until O_PATH at least - to
open a file without any permission; O_RDONLY was always implied on the
uapi side while the kernel does in fact allow opening files without
permissions.

The trouble comes when trying to map the uapi flags onto the
corresponding file mode flags FMODE_{READ,WRITE}. This mapping still
happens today and is causing issues to this day (We ran into this
during additions for openat2() for example.).

So the special value "3" was used to indicate that the file was opened
for special access:

    f->f_flags = flag = flags;
    f->f_mode = (flag+1) & O_ACCMODE;
    if (f->f_mode)
            flag++;

This allowed the file mode to be set to FMODE_READ | FMODE_WRITE mapping
the O_{RDONLY,WRONLY,RDWR} flags into the FMODE_{READ,WRITE} flags. The
special access then required read-write permissions and 0 was used to
access symlinks.

But back when ddc733f4 ("[PATCH] Linux-0.97 (August 1, 1992)") added
coredump handling open_namei() took the FMODE_{READ,WRITE} flags as an
argument. So the coredump handling introduced in
ddc733f4 ("[PATCH] Linux-0.97 (August 1, 1992)") was buggy because
O_WRONLY shouldn't have been passed. Since O_WRONLY is 1 but
open_namei() took FMODE_{READ,WRITE} it was passed FMODE_READ on
accident.

So 9cb9f18b ("[PATCH] Linux-0.99.10 (June 7, 1993)") was a bugfix
for this and the 2 didn't really mean O_RDWR, it meant FMODE_WRITE which
was correct.

The clue is that FMODE_{READ,WRITE} didn't exist yet and thus a raw "2"
value was passed.

Fast forward 5 years when around 2.2.4pre4 (February 16, 1999) this code
was changed to:

    -       dentry = open_namei(corefile,O_CREAT | 2 | O_TRUNC | O_NOFOLLOW, 0600);
    ...
    +       file = filp_open(corefile,O_CREAT | 2 | O_TRUNC | O_NOFOLLOW, 0600);

At this point the raw "2" should have become O_WRONLY again as
filp_open() didn't take FMODE_{READ,WRITE} but O_{RDONLY,WRONLY,RDWR}.

Another 17 years later, the code was changed again cementing the mistake
and making it almost impossible to detect when commit
378c6520 ("fs/coredump: prevent fsuid=0 dumps into user-controlled directories")
replaced the raw "2" with O_RDWR.

And now, here we are with this patch that sent us on a quest to answer
the big questions in life such as "Why are coredump files opened with
O_RDWR?" and "Is it safe to just use O_WRONLY?".

So with this commit we're reintroducing O_WRONLY again and bringing this
code back to its original state when it was first introduced in commit
ddc733f4 ("[PATCH] Linux-0.97 (August 1, 1992)") over 30 years ago.
Signed-off-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-Id: <20230420120409.602576-1-vsementsov@yandex-team.ru>
[brauner@kernel.org: completely rewritten commit message]
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      88e46070
  5. 15 May, 2023 5 commits
  7. 14 May, 2023 13 commits
  9. 13 May, 2023 17 commits
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