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authorDave Martin <Dave.Martin@arm.com>2018-06-07 14:32:05 +0300
committerCatalin Marinas <catalin.marinas@arm.com>2018-06-08 15:21:39 +0300
commit0fe42512b2f03f9e5a20b9f55ef1013a68b4cd48 (patch)
tree3afaea68ef0f23eae6cf6dd57eaf1a83d09350d5
parente156ab71a974737c279530e3b868131291fe677e (diff)
downloadlinux-0fe42512b2f03f9e5a20b9f55ef1013a68b4cd48.tar.xz
arm64: Fix syscall restarting around signal suppressed by tracer
Commit 17c2895 ("arm64: Abstract syscallno manipulation") abstracts out the pt_regs.syscallno value for a syscall cancelled by a tracer as NO_SYSCALL, and provides helpers to set and check for this condition. However, the way this was implemented has the unintended side-effect of disabling part of the syscall restart logic. This comes about because the second in_syscall() check in do_signal() re-evaluates the "in a syscall" condition based on the updated pt_regs instead of the original pt_regs. forget_syscall() is explicitly called prior to the second check in order to prevent restart logic in the ret_to_user path being spuriously triggered, which means that the second in_syscall() check always yields false. This triggers a failure in tools/testing/selftests/seccomp/seccomp_bpf.c, when using ptrace to suppress a signal that interrups a nanosleep() syscall. Misbehaviour of this type is only expected in the case where a tracer suppresses a signal and the target process is either being single-stepped or the interrupted syscall attempts to restart via -ERESTARTBLOCK. This patch restores the old behaviour by performing the in_syscall() check only once at the start of the function. Fixes: 17c289586009 ("arm64: Abstract syscallno manipulation") Signed-off-by: Dave Martin <Dave.Martin@arm.com> Reported-by: Sumit Semwal <sumit.semwal@linaro.org> Cc: Will Deacon <will.deacon@arm.com> Cc: <stable@vger.kernel.org> # 4.14.x- Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
-rw-r--r--arch/arm64/kernel/signal.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index e7da5dba7ba8..511af13e8d8f 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -843,11 +843,12 @@ static void do_signal(struct pt_regs *regs)
unsigned long continue_addr = 0, restart_addr = 0;
int retval = 0;
struct ksignal ksig;
+ bool syscall = in_syscall(regs);
/*
* If we were from a system call, check for system call restarting...
*/
- if (in_syscall(regs)) {
+ if (syscall) {
continue_addr = regs->pc;
restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
retval = regs->regs[0];
@@ -899,7 +900,7 @@ static void do_signal(struct pt_regs *regs)
* Handle restarting a different system call. As above, if a debugger
* has chosen to restart at a different PC, ignore the restart.
*/
- if (in_syscall(regs) && regs->pc == restart_addr) {
+ if (syscall && regs->pc == restart_addr) {
if (retval == -ERESTART_RESTARTBLOCK)
setup_restart_syscall(regs);
user_rewind_single_step(current);