signal: fix information leak in copy_siginfo_to_user

commit 26135022f85105ad725cda103fa069e29e83bd16 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c
index 7ed72dc0fb0eba6bea2c1456c8d51ac80e551fa0..624e993a4a06f59fb85e09541e31cc5d239e1a57 100644 (file)
--- a/arch/arm64/kernel/signal32.c
+++ b/arch/arm64/kernel/signal32.c
@@ -165,7 +165,8 @@ int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
                 * Other callers might not initialize the si_lsb field,
                 * so check explicitely 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
                break;

diff --git a/kernel/signal.c b/kernel/signal.c
index 52f881db1ca02a4190b46174e5d7ad458c7b5c33..7e44cdf43cc130a623fe4d140d0d402fa16d4495 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2768,7 +2768,8 @@ int copy_siginfo_to_user(siginfo_t __user *to, const siginfo_t *from)
                 * 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
                break;