Patch "signalfd: fix information leak in signalfd_copyinfo" has been added to the 4.1-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    signalfd: fix information leak in signalfd_copyinfo

to the 4.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     signalfd-fix-information-leak-in-signalfd_copyinfo.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 3ead7c52bdb0ab44f4bb1feed505a8323cc12ba7 Mon Sep 17 00:00:00 2001
From: Amanieu d'Antras <amanieu@gmail.com>
Date: Thu, 6 Aug 2015 15:46:33 -0700
Subject: signalfd: fix information leak in signalfd_copyinfo

From: Amanieu d'Antras <amanieu@gmail.com>

commit 3ead7c52bdb0ab44f4bb1feed505a8323cc12ba7 upstream.

This function may copy the si_addr_lsb field to user mode when it hasn't
been initialized, which can leak kernel stack data to user mode.

Just checking the value of si_code is insufficient because the same
si_code value is shared between multiple signals.  This is solved by
checking the value of si_signo in addition to si_code.

Signed-off-by: Amanieu d'Antras <amanieu@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/signalfd.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/fs/signalfd.c
+++ b/fs/signalfd.c
@@ -121,8 +121,9 @@ static int signalfd_copyinfo(struct sign
 		 * Other callers might not initialize the si_lsb field,
 		 * so check explicitly for the right codes here.
 		 */
-		if (kinfo->si_code == BUS_MCEERR_AR ||
-		    kinfo->si_code == BUS_MCEERR_AO)
+		if (kinfo->si_signo == SIGBUS &&
+		    (kinfo->si_code == BUS_MCEERR_AR ||
+		     kinfo->si_code == BUS_MCEERR_AO))
 			err |= __put_user((short) kinfo->si_addr_lsb,
 					  &uinfo->ssi_addr_lsb);
 #endif


Patches currently in stable-queue which might be from amanieu@gmail.com are

queue-4.1/signal-fix-information-leak-in-copy_siginfo_from_user32.patch
queue-4.1/signal-fix-information-leak-in-copy_siginfo_to_user.patch
queue-4.1/signalfd-fix-information-leak-in-signalfd_copyinfo.patch