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.
Cc: Christopher M. Riedl cmr@bluescreens.de Fixes: 887f3ceb51cd ("powerpc/signal32: Convert do_setcontext[_tm]() to user access block") Cc: stable@vger.kernel.org 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 --- arch/powerpc/kernel/signal.h | 10 ++++++++-- 1 file 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,