signal: fix information leak in copy_siginfo_to_user
This function may copy the si_addr_lsb, si_lower and si_upper fields to
user mode when they haven'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>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/signal.c b/kernel/signal.c
index 00524cf..0f6bbbe 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2748,12 +2748,15 @@
* Other callers might not initialize the si_lsb field,
* so check explicitly for the right codes here.
*/
- if (from->si_code == BUS_MCEERR_AR || from->si_code == BUS_MCEERR_AO)
+ if (from->si_signo == SIGBUS &&
+ (from->si_code == BUS_MCEERR_AR || from->si_code == BUS_MCEERR_AO))
err |= __put_user(from->si_addr_lsb, &to->si_addr_lsb);
#endif
#ifdef SEGV_BNDERR
- err |= __put_user(from->si_lower, &to->si_lower);
- err |= __put_user(from->si_upper, &to->si_upper);
+ if (from->si_signo == SIGSEGV && from->si_code == SEGV_BNDERR) {
+ err |= __put_user(from->si_lower, &to->si_lower);
+ err |= __put_user(from->si_upper, &to->si_upper);
+ }
#endif
break;
case __SI_CHLD: