unix: correctly track in-flight fds in sending process user_struct
commit 415e3d3e90ce9e18727e8843ae343eda5a58fad6 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:
712f4aad406bb1 ("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>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Change-Id: I730fe126b5824c90a72b17f363237493c8916634
5 files changed