[PATCH 6.4 107/737] ARM: ptrace: Restore syscall restart tracing

[Greg Kroah-Hartman]

6.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kees Cook <keescook at chromium.org>

[ Upstream commit cf007647475b5090819c5fe8da771073145c7334 ]

Since commit 4e57a4ddf6b0 ("ARM: 9107/1: syscall: always store
thread_info->abi_syscall"), the seccomp selftests "syscall_restart" has
been broken. This was caused by the restart syscall not being stored to
"abi_syscall" during restart setup before branching to the "local_restart"
label. Tracers would see the wrong syscall, and scno would get overwritten
while returning from the TIF_WORK path. Add the missing store.

Cc: Russell King <linux at armlinux.org.uk>
Cc: Arnd Bergmann <arnd at kernel.org>
Cc: Lecopzer Chen <lecopzer.chen at mediatek.com>
Cc: Oleg Nesterov <oleg at redhat.com>
Cc: linux-arm-kernel at lists.infradead.org
Fixes: 4e57a4ddf6b0 ("ARM: 9107/1: syscall: always store thread_info->abi_syscall")
Reviewed-by: Arnd Bergmann <arnd at arndb.de>
Link: https://lore.kernel.org/r/20230810195422.2304827-1-keescook@chromium.org
Signed-off-by: Kees Cook <keescook at chromium.org>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 arch/arm/kernel/entry-common.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 03d4c5578c5c9..b60bba3c1d516 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -90,6 +90,7 @@ slow_work_pending:
 	cmp	r0, #0
 	beq	no_work_pending
 	movlt	scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE)
+	str	scno, [tsk, #TI_ABI_SYSCALL]	@ make sure tracers see update
 	ldmia	sp, {r0 - r6}			@ have to reload r0 - r6
 	b	local_restart			@ ... and off we go
 ENDPROC(ret_fast_syscall)
-- 
2.40.1