signalfd: fix information leak in signalfd_copyinfo
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>
diff --git a/fs/signalfd.c b/fs/signalfd.c
index 7e412ad..270221f 100644
--- a/fs/signalfd.c
+++ b/fs/signalfd.c
@@ -121,8 +121,9 @@
* 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
