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ARC: [Review] Prevent incorrect syscall restarts

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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>
This commit is contained in:
Vineet Gupta 2013-01-18 15:12:19 +05:30
parent 5c39c0ab5e
commit 55bb9480f9
2 changed files with 11 additions and 4 deletions
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3
arch/arc/include/asm/ptrace.h
View File

@ -100,6 +100,9 @@ struct callee_regs {
#define in_syscall(regs) (regs->event & orig_r8_IS_SCALL) #define in_syscall(regs) (regs->event & orig_r8_IS_SCALL)
#define in_brkpt_trap(regs) (regs->event & orig_r8_IS_BRKPT) #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() \ #define current_pt_regs() \
({ \ ({ \
/* open-coded current_thread_info() */ \ /* open-coded current_thread_info() */ \

12
arch/arc/kernel/signal.c
View File

@ -128,6 +128,9 @@ SYSCALL_DEFINE0(rt_sigreturn)
if (restore_altstack(&sf->uc.uc_stack)) if (restore_altstack(&sf->uc.uc_stack))
goto badframe; goto badframe;
/* Don't restart from sigreturn */
syscall_wont_restart(regs);
return regs->r0; return regs->r0;
badframe: badframe:
@ -318,13 +321,13 @@ void do_signal(struct pt_regs *regs)
signr = get_signal_to_deliver(&info, &ka, regs, NULL); signr = get_signal_to_deliver(&info, &ka, regs, NULL);
/* Are we from a system call? */ restart_scall = in_syscall(regs) && syscall_restartable(regs);
restart_scall = in_syscall(regs);
if (signr > 0) { if (signr > 0) {
if (restart_scall) if (restart_scall) {
arc_restart_syscall(&ka, regs); arc_restart_syscall(&ka, regs);
syscall_wont_restart(regs); /* No more restarts */
}
handle_signal(signr, &ka, &info, regs); handle_signal(signr, &ka, &info, regs);
return; return;
} }
@ -339,6 +342,7 @@ void do_signal(struct pt_regs *regs)
regs->r8 = __NR_restart_syscall; regs->r8 = __NR_restart_syscall;
regs->ret -= 4; regs->ret -= 4;
} }
syscall_wont_restart(regs); /* No more restarts */
} }
/* If there's no signal to deliver, restore the saved sigmask back */ /* If there's no signal to deliver, restore the saved sigmask back */