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Commit 26135022 authored Aug 06, 2015 by Amanieu d'Antras Committed by Linus Torvalds Aug 07, 2015

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>

parent 3c00cb5e

arch/arm64/kernel/signal32.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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;

kernel/signal.c

+6 −3

Original line number	Diff line number	Diff line
		@@ -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
		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: