diff options
| author | Al Viro <viro@zeniv.linux.org.uk> | 2021-06-30 18:56:43 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-07-01 11:06:06 -0700 |
| commit | 97c885d585c53d3f1ad4545b0ee10f0bdfaa1a4d (patch) | |
| tree | 7cde905a1c673d67360873c93eb017078382af09 | |
| parent | c3eb84092b326a353725edcc8274a3782f1d1524 (diff) | |
x86: signal: don't do sas_ss_reset() until we are certain that sigframe won't be abandoned
Currently we handle SS_AUTODISARM as soon as we have stored the altstack
settings into sigframe - that's the point when we have set the things up
for eventual sigreturn to restore the old settings. And if we manage to
set the sigframe up (we are not done with that yet), everything's fine.
However, in case of failure we end up with sigframe-to-be abandoned and
SIGSEGV force-delivered. And in that case we end up with inconsistent
rules - late failures have altstack reset, early ones do not.
It's trivial to get consistent behaviour - just handle SS_AUTODISARM once
we have set the sigframe up and are committed to entering the handler,
i.e. in signal_delivered().
Link: https://lore.kernel.org/lkml/20200404170604.GN23230@ZenIV.linux.org.uk/
Link: https://github.com/ClangBuiltLinux/linux/issues/876
Link: https://lkml.kernel.org/r/20210422230846.1756380-1-ndesaulniers@google.com
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | include/linux/compat.h | 2 | ||||
| -rw-r--r-- | include/linux/signal.h | 2 | ||||
| -rw-r--r-- | kernel/signal.c | 14 |
3 files changed, 4 insertions, 14 deletions
diff --git a/include/linux/compat.h b/include/linux/compat.h index 8855b1b702b2..c270124e4402 100644 --- a/include/linux/compat.h +++ b/include/linux/compat.h @@ -532,8 +532,6 @@ int __compat_save_altstack(compat_stack_t __user *, unsigned long); &__uss->ss_sp, label); \ unsafe_put_user(t->sas_ss_flags, &__uss->ss_flags, label); \ unsafe_put_user(t->sas_ss_size, &__uss->ss_size, label); \ - if (t->sas_ss_flags & SS_AUTODISARM) \ - sas_ss_reset(t); \ } while (0); /* diff --git a/include/linux/signal.h b/include/linux/signal.h index 5160fd45e5ca..3454c7ff0778 100644 --- a/include/linux/signal.h +++ b/include/linux/signal.h @@ -462,8 +462,6 @@ int __save_altstack(stack_t __user *, unsigned long); unsafe_put_user((void __user *)t->sas_ss_sp, &__uss->ss_sp, label); \ unsafe_put_user(t->sas_ss_flags, &__uss->ss_flags, label); \ unsafe_put_user(t->sas_ss_size, &__uss->ss_size, label); \ - if (t->sas_ss_flags & SS_AUTODISARM) \ - sas_ss_reset(t); \ } while (0); #ifdef CONFIG_PROC_FS diff --git a/kernel/signal.c b/kernel/signal.c index 30a0bee5ff9b..6b4df88cc630 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2829,6 +2829,8 @@ static void signal_delivered(struct ksignal *ksig, int stepping) if (!(ksig->ka.sa.sa_flags & SA_NODEFER)) sigaddset(&blocked, ksig->sig); set_current_blocked(&blocked); + if (current->sas_ss_flags & SS_AUTODISARM) + sas_ss_reset(current); tracehook_signal_handler(stepping); } @@ -4147,11 +4149,7 @@ int __save_altstack(stack_t __user *uss, unsigned long sp) int err = __put_user((void __user *)t->sas_ss_sp, &uss->ss_sp) | __put_user(t->sas_ss_flags, &uss->ss_flags) | __put_user(t->sas_ss_size, &uss->ss_size); - if (err) - return err; - if (t->sas_ss_flags & SS_AUTODISARM) - sas_ss_reset(t); - return 0; + return err; } #ifdef CONFIG_COMPAT @@ -4206,11 +4204,7 @@ int __compat_save_altstack(compat_stack_t __user *uss, unsigned long sp) &uss->ss_sp) | __put_user(t->sas_ss_flags, &uss->ss_flags) | __put_user(t->sas_ss_size, &uss->ss_size); - if (err) - return err; - if (t->sas_ss_flags & SS_AUTODISARM) - sas_ss_reset(t); - return 0; + return err; } #endif |