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signal: fix information leak in copy_siginfo_to_user

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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>
This commit is contained in:
Amanieu d'Antras 2015-08-06 15:46:29 -07:00 committed by Linus Torvalds
parent 3c00cb5e68
commit 26135022f8
2 changed files with 8 additions and 4 deletions
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3
arch/arm64/kernel/signal32.c
View file

@ -168,7 +168,8 @@ 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;

9
kernel/signal.c
View file

@ -2748,12 +2748,15 @@ 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
#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: