Commit 849151dd authored by Thomas Gleixner's avatar Thomas Gleixner

compat: nanosleep: Clarify error handling

The error handling in compat_sys_nanosleep() is correct, but
completely non obvious. Document it and restrict it to the
-ERESTART_RESTARTBLOCK return value for clarity.
Reported-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 40bea039
...@@ -226,7 +226,7 @@ static long compat_nanosleep_restart(struct restart_block *restart) ...@@ -226,7 +226,7 @@ static long compat_nanosleep_restart(struct restart_block *restart)
ret = hrtimer_nanosleep_restart(restart); ret = hrtimer_nanosleep_restart(restart);
set_fs(oldfs); set_fs(oldfs);
if (ret) { if (ret == -ERESTART_RESTARTBLOCK) {
rmtp = restart->nanosleep.compat_rmtp; rmtp = restart->nanosleep.compat_rmtp;
if (rmtp && compat_put_timespec(&rmt, rmtp)) if (rmtp && compat_put_timespec(&rmt, rmtp))
...@@ -256,7 +256,26 @@ COMPAT_SYSCALL_DEFINE2(nanosleep, struct compat_timespec __user *, rqtp, ...@@ -256,7 +256,26 @@ COMPAT_SYSCALL_DEFINE2(nanosleep, struct compat_timespec __user *, rqtp,
HRTIMER_MODE_REL, CLOCK_MONOTONIC); HRTIMER_MODE_REL, CLOCK_MONOTONIC);
set_fs(oldfs); set_fs(oldfs);
if (ret) { /*
* hrtimer_nanosleep() can only return 0 or
* -ERESTART_RESTARTBLOCK here because:
*
* - we call it with HRTIMER_MODE_REL and therefor exclude the
* -ERESTARTNOHAND return path.
*
* - we supply the rmtp argument from the task stack (due to
* the necessary compat conversion. So the update cannot
* fail, which excludes the -EFAULT return path as well. If
* it fails nevertheless we have a bigger problem and wont
* reach this place anymore.
*
* - if the return value is 0, we do not have to update rmtp
* because there is no remaining time.
*
* We check for -ERESTART_RESTARTBLOCK nevertheless if the
* core implementation decides to return random nonsense.
*/
if (ret == -ERESTART_RESTARTBLOCK) {
struct restart_block *restart struct restart_block *restart
= &current_thread_info()->restart_block; = &current_thread_info()->restart_block;
...@@ -266,7 +285,6 @@ COMPAT_SYSCALL_DEFINE2(nanosleep, struct compat_timespec __user *, rqtp, ...@@ -266,7 +285,6 @@ COMPAT_SYSCALL_DEFINE2(nanosleep, struct compat_timespec __user *, rqtp,
if (rmtp && compat_put_timespec(&rmt, rmtp)) if (rmtp && compat_put_timespec(&rmt, rmtp))
return -EFAULT; return -EFAULT;
} }
return ret; return ret;
} }
......
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