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signalfd: fix information leak in signalfd_copyinfo

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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>
This commit is contained in:
Amanieu d'Antras 2015-08-06 15:46:33 -07:00 committed by Linus Torvalds
parent 26135022f8
commit 3ead7c52bd
1 changed files with 3 additions and 2 deletions
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5
fs/signalfd.c
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@ -121,8 +121,9 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
* Other callers might not initialize the si_lsb field, * Other callers might not initialize the si_lsb field,
* so check explicitly for the right codes here. * so check explicitly for the right codes here.
*/ */
if (kinfo->si_code == BUS_MCEERR_AR || if (kinfo->si_signo == SIGBUS &&
kinfo->si_code == BUS_MCEERR_AO) (kinfo->si_code == BUS_MCEERR_AR ||
kinfo->si_code == BUS_MCEERR_AO))
err |= __put_user((short) kinfo->si_addr_lsb, err |= __put_user((short) kinfo->si_addr_lsb,
&uinfo->ssi_addr_lsb); &uinfo->ssi_addr_lsb);
#endif #endif