Commit 03c70599 authored by Hannes Frederic Sowa's avatar Hannes Frederic Sowa Committed by Luis Henriques

unix: correctly track in-flight fds in sending process user_struct

commit 415e3d3e upstream.

The commit referenced in the Fixes tag incorrectly accounted the number
of in-flight fds over a unix domain socket to the original opener
of the file-descriptor. This allows another process to arbitrary
deplete the original file-openers resource limit for the maximum of
open files. Instead the sending processes and its struct cred should
be credited.

To do so, we add a reference counted struct user_struct pointer to the
scm_fp_list and use it to account for the number of inflight unix fds.

Fixes: 712f4aad ("unix: properly account for FDs passed over unix sockets")
Reported-by: default avatarDavid Herrmann <dh.herrmann@gmail.com>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent c501d329
...@@ -6,8 +6,8 @@ ...@@ -6,8 +6,8 @@
#include <linux/mutex.h> #include <linux/mutex.h>
#include <net/sock.h> #include <net/sock.h>
void unix_inflight(struct file *fp); void unix_inflight(struct user_struct *user, struct file *fp);
void unix_notinflight(struct file *fp); void unix_notinflight(struct user_struct *user, struct file *fp);
void unix_gc(void); void unix_gc(void);
void wait_for_unix_gc(void); void wait_for_unix_gc(void);
struct sock *unix_get_socket(struct file *filp); struct sock *unix_get_socket(struct file *filp);
......
...@@ -21,6 +21,7 @@ struct scm_creds { ...@@ -21,6 +21,7 @@ struct scm_creds {
struct scm_fp_list { struct scm_fp_list {
short count; short count;
short max; short max;
struct user_struct *user;
struct file *fp[SCM_MAX_FD]; struct file *fp[SCM_MAX_FD];
}; };
......
...@@ -87,6 +87,7 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) ...@@ -87,6 +87,7 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
*fplp = fpl; *fplp = fpl;
fpl->count = 0; fpl->count = 0;
fpl->max = SCM_MAX_FD; fpl->max = SCM_MAX_FD;
fpl->user = NULL;
} }
fpp = &fpl->fp[fpl->count]; fpp = &fpl->fp[fpl->count];
...@@ -107,6 +108,10 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) ...@@ -107,6 +108,10 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
*fpp++ = file; *fpp++ = file;
fpl->count++; fpl->count++;
} }
if (!fpl->user)
fpl->user = get_uid(current_user());
return num; return num;
} }
...@@ -119,6 +124,7 @@ void __scm_destroy(struct scm_cookie *scm) ...@@ -119,6 +124,7 @@ void __scm_destroy(struct scm_cookie *scm)
scm->fp = NULL; scm->fp = NULL;
for (i=fpl->count-1; i>=0; i--) for (i=fpl->count-1; i>=0; i--)
fput(fpl->fp[i]); fput(fpl->fp[i]);
free_uid(fpl->user);
kfree(fpl); kfree(fpl);
} }
} }
...@@ -337,6 +343,7 @@ struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) ...@@ -337,6 +343,7 @@ struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
for (i = 0; i < fpl->count; i++) for (i = 0; i < fpl->count; i++)
get_file(fpl->fp[i]); get_file(fpl->fp[i]);
new_fpl->max = new_fpl->count; new_fpl->max = new_fpl->count;
new_fpl->user = get_uid(fpl->user);
} }
return new_fpl; return new_fpl;
} }
......
...@@ -1469,7 +1469,7 @@ static void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb) ...@@ -1469,7 +1469,7 @@ static void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb)
UNIXCB(skb).fp = NULL; UNIXCB(skb).fp = NULL;
for (i = scm->fp->count-1; i >= 0; i--) for (i = scm->fp->count-1; i >= 0; i--)
unix_notinflight(scm->fp->fp[i]); unix_notinflight(scm->fp->user, scm->fp->fp[i]);
} }
static void unix_destruct_scm(struct sk_buff *skb) static void unix_destruct_scm(struct sk_buff *skb)
...@@ -1534,7 +1534,7 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb) ...@@ -1534,7 +1534,7 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
return -ENOMEM; return -ENOMEM;
for (i = scm->fp->count - 1; i >= 0; i--) for (i = scm->fp->count - 1; i >= 0; i--)
unix_inflight(scm->fp->fp[i]); unix_inflight(scm->fp->user, scm->fp->fp[i]);
return max_level; return max_level;
} }
......
...@@ -122,7 +122,7 @@ struct sock *unix_get_socket(struct file *filp) ...@@ -122,7 +122,7 @@ struct sock *unix_get_socket(struct file *filp)
* descriptor if it is for an AF_UNIX socket. * descriptor if it is for an AF_UNIX socket.
*/ */
void unix_inflight(struct file *fp) void unix_inflight(struct user_struct *user, struct file *fp)
{ {
struct sock *s = unix_get_socket(fp); struct sock *s = unix_get_socket(fp);
...@@ -139,11 +139,11 @@ void unix_inflight(struct file *fp) ...@@ -139,11 +139,11 @@ void unix_inflight(struct file *fp)
} }
unix_tot_inflight++; unix_tot_inflight++;
} }
fp->f_cred->user->unix_inflight++; user->unix_inflight++;
spin_unlock(&unix_gc_lock); spin_unlock(&unix_gc_lock);
} }
void unix_notinflight(struct file *fp) void unix_notinflight(struct user_struct *user, struct file *fp)
{ {
struct sock *s = unix_get_socket(fp); struct sock *s = unix_get_socket(fp);
...@@ -157,7 +157,7 @@ void unix_notinflight(struct file *fp) ...@@ -157,7 +157,7 @@ void unix_notinflight(struct file *fp)
list_del_init(&u->link); list_del_init(&u->link);
unix_tot_inflight--; unix_tot_inflight--;
} }
fp->f_cred->user->unix_inflight--; user->unix_inflight--;
spin_unlock(&unix_gc_lock); spin_unlock(&unix_gc_lock);
} }
......
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