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

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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: 712f4aad40 ("unix: properly account for FDs passed over unix sockets")
Reported-by: David 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: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Hannes Frederic Sowa 2016-02-03 02:11:03 +01:00 • committed by David S. Miller
parent aa7b453780
commit 415e3d3e90
5 changed files with 16 additions and 8 deletions
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8
net/unix/garbage.c
View file

@ -116,7 +116,7 @@ struct sock *unix_get_socket(struct file *filp)
* 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);
@ -133,11 +133,11 @@ void unix_inflight(struct file *fp)
}
unix_tot_inflight++;
}
fp->f_cred->user->unix_inflight++;
user->unix_inflight++;
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);
@ -152,7 +152,7 @@ void unix_notinflight(struct file *fp)
list_del_init(&u->link);
unix_tot_inflight--;
}
fp->f_cred->user->unix_inflight--;
user->unix_inflight--;
spin_unlock(&unix_gc_lock);
}