From: Christophe Leroy <christophe.le...@csgroup.eu> The conversion from __copy_from_user() to __get_user() introduced a regression in __get_user_sigset() in v5.13. The bug was subsequently copied and pasted in unsafe_get_user_sigset().
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 casting the __get_user() assignment lvalue to u64 so that the entire struct gets copied. Cc: Christophe Leroy <christophe.le...@csgroup.eu> Cc: Christopher M. Riedl <c...@bluescreens.de> Link: https://lore.kernel.org/linuxppc-dev/FEtBUOuFPMN4zJy4bIOqz6C4xoliCbTxS7VtMKD6UZkbvEbycUceRgGAd7e9-trRdwVN3hWAbQi0qrNx8Zgn8niTQf2KPVdw-W35czDIaeQ=@protonmail.com/ Fixes: 887f3ceb51cd ("powerpc/signal32: Convert do_setcontext[_tm]() to user access block") Fixes: d3ccc9781560 ("powerpc/signal: Use __get_user() to copy sigset_t") Reported-and-tested-by: Stan Johnson <user...@yahoo.com> Signed-off-by: Finn Thain <fth...@linux-m68k.org> --- Christophe, I hope this change is the one you wanted to see upstream (?). If it is acceptable please add your signed-off-by tag. --- arch/powerpc/kernel/signal.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/signal.h b/arch/powerpc/kernel/signal.h index 1f07317964e4..44e736b88e91 100644 --- a/arch/powerpc/kernel/signal.h +++ b/arch/powerpc/kernel/signal.h @@ -23,10 +23,10 @@ static inline int __get_user_sigset(sigset_t *dst, const sigset_t __user *src) { BUILD_BUG_ON(sizeof(sigset_t) != sizeof(u64)); - return __get_user(dst->sig[0], (u64 __user *)&src->sig[0]); + return __get_user(*(u64 *)&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) + unsafe_get_user(*(u64 *)&(dst)->sig[0], (u64 __user *)&(src)->sig[0], label) #ifdef CONFIG_VSX extern unsigned long copy_vsx_to_user(void __user *to, -- 2.26.3