diff options
author | Dave Martin <Dave.Martin@arm.com> | 2018-06-07 12:32:05 +0100 |
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committer | Catalin Marinas <catalin.marinas@arm.com> | 2018-06-08 13:21:39 +0100 |
commit | 0fe42512b2f03f9e5a20b9f55ef1013a68b4cd48 (patch) | |
tree | 3afaea68ef0f23eae6cf6dd57eaf1a83d09350d5 /arch | |
parent | e156ab71a974737c279530e3b868131291fe677e (diff) | |
download | linux-0fe42512b2f03f9e5a20b9f55ef1013a68b4cd48.tar.bz2 |
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>
Diffstat (limited to 'arch')
-rw-r--r-- | arch/arm64/kernel/signal.c | 5 |
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); |