diff options
| author | Christophe Leroy <christophe.leroy@csgroup.eu> | 2021-11-15 09:52:55 +0100 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2021-11-16 21:24:16 +1100 |
| commit | 5499802b2284331788a440585869590f1bd63f7f (patch) | |
| tree | 743af68b66d6fae7ca23861634f4f88aea0e3e10 /arch/powerpc/kernel/signal.h | |
| parent | 5b54860943dc4681be5de2fc287408c7ce274dfc (diff) | |
powerpc/signal32: Fix sigset_t copy
The conversion from __copy_from_user() to __get_user() by
commit d3ccc9781560 ("powerpc/signal: Use __get_user() to copy
sigset_t") introduced a regression in __get_user_sigset() for
powerpc/32. The bug was subsequently moved into
unsafe_get_user_sigset().
The bug is due to the copied 64 bit value being truncated to
32 bits while being assigned to dst->sig[0]
The regression was reported by users of the Xorg packages distributed in
Debian/powerpc --
"The symptoms are that the fb screen goes blank, with the backlight
remaining on and no errors logged in /var/log; wdm (or startx) run
with no effect (I tried logging in in the blind, with no effect).
And they are hard to kill, requiring 'kill -KILL ...'"
Fix the regression by copying each word of the sigset, not only the
first one.
__get_user_sigset() was tentatively optimised to copy 64 bits at once
in order to minimise KUAP unlock/lock impact, but the unsafe variant
doesn't suffer that, so it can just copy words.
Fixes: 887f3ceb51cd ("powerpc/signal32: Convert do_setcontext[_tm]() to user access block")
Cc: stable@vger.kernel.org # v5.13+
Reported-by: Finn Thain <fthain@linux-m68k.org>
Reported-and-tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/99ef38d61c0eb3f79c68942deb0c35995a93a777.1636966353.git.christophe.leroy@csgroup.eu
Diffstat (limited to 'arch/powerpc/kernel/signal.h')
| -rw-r--r-- | arch/powerpc/kernel/signal.h | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/signal.h b/arch/powerpc/kernel/signal.h index 1f07317964e4..618aeccdf691 100644 --- a/arch/powerpc/kernel/signal.h +++ b/arch/powerpc/kernel/signal.h @@ -25,8 +25,14 @@ static inline int __get_user_sigset(sigset_t *dst, const sigset_t __user *src) return __get_user(dst->sig[0], (u64 __user *)&src->sig[0]); } -#define unsafe_get_user_sigset(dst, src, label) \ - unsafe_get_user((dst)->sig[0], (u64 __user *)&(src)->sig[0], label) +#define unsafe_get_user_sigset(dst, src, label) do { \ + sigset_t *__dst = dst; \ + const sigset_t __user *__src = src; \ + int i; \ + \ + for (i = 0; i < _NSIG_WORDS; i++) \ + unsafe_get_user(__dst->sig[i], &__src->sig[i], label); \ +} while (0) #ifdef CONFIG_VSX extern unsigned long copy_vsx_to_user(void __user *to, |