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| author | Vineet Gupta <vgupta@synopsys.com> | 2013-01-18 10:42:19 +0100 |
|---|---|---|
| committer | Vineet Gupta <vgupta@synopsys.com> | 2013-02-15 18:45:50 +0100 |
| commit | 55bb9480f9159b229ac3c3454c97b62d1e0a7e80 (patch) | |
| tree | 4de8a97445bb41f250cdadba78169d0463bd244b | |
| parent | ARC: [Review] Preparing to fix incorrect syscall restarts due to signals (diff) | |
| download | linux-55bb9480f9159b229ac3c3454c97b62d1e0a7e80.tar.xz linux-55bb9480f9159b229ac3c3454c97b62d1e0a7e80.zip | |
ARC: [Review] Prevent incorrect syscall restarts
Per Al Viro's "signals for dummies" https://lkml.org/lkml/2012/12/6/366
there are 3 golden rules for (not) restarting syscalls:
" What we need to guarantee is
* restarts do not happen on signals caught in interrupts or exceptions
* restarts do not happen on signals caught in sigreturn()
* restart should happen only once, even if we get through do_signal()
many times."
ARC Port already handled #1, this patch fixes #2 and #3.
We use the additional state in pt_regs->orig_r8 to ckh if restarting
has already been done once.
Thanks to Al Viro for spotting this.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
| -rw-r--r-- | arch/arc/include/asm/ptrace.h | 3 | ||||
| -rw-r--r-- | arch/arc/kernel/signal.c | 12 |
2 files changed, 11 insertions, 4 deletions
diff --git a/arch/arc/include/asm/ptrace.h b/arch/arc/include/asm/ptrace.h index 3ec89f467ac3..a98957a95fb3 100644 --- a/arch/arc/include/asm/ptrace.h +++ b/arch/arc/include/asm/ptrace.h @@ -100,6 +100,9 @@ struct callee_regs { #define in_syscall(regs) (regs->event & orig_r8_IS_SCALL) #define in_brkpt_trap(regs) (regs->event & orig_r8_IS_BRKPT) +#define syscall_wont_restart(regs) (regs->event |= orig_r8_IS_SCALL_RESTARTED) +#define syscall_restartable(regs) !(regs->event & orig_r8_IS_SCALL_RESTARTED) + #define current_pt_regs() \ ({ \ /* open-coded current_thread_info() */ \ diff --git a/arch/arc/kernel/signal.c b/arch/arc/kernel/signal.c index ab8ed5a55461..ee6ef2f60a28 100644 --- a/arch/arc/kernel/signal.c +++ b/arch/arc/kernel/signal.c @@ -128,6 +128,9 @@ SYSCALL_DEFINE0(rt_sigreturn) if (restore_altstack(&sf->uc.uc_stack)) goto badframe; + /* Don't restart from sigreturn */ + syscall_wont_restart(regs); + return regs->r0; badframe: @@ -318,13 +321,13 @@ void do_signal(struct pt_regs *regs) signr = get_signal_to_deliver(&info, &ka, regs, NULL); - /* Are we from a system call? */ - restart_scall = in_syscall(regs); + restart_scall = in_syscall(regs) && syscall_restartable(regs); if (signr > 0) { - if (restart_scall) + if (restart_scall) { arc_restart_syscall(&ka, regs); - + syscall_wont_restart(regs); /* No more restarts */ + } handle_signal(signr, &ka, &info, regs); return; } @@ -339,6 +342,7 @@ void do_signal(struct pt_regs *regs) regs->r8 = __NR_restart_syscall; regs->ret -= 4; } + syscall_wont_restart(regs); /* No more restarts */ } /* If there's no signal to deliver, restore the saved sigmask back */ |