From eb3a72921c8276bf2cd028a458bb83435f16c91c Mon Sep 17 00:00:00 2001 From: Keshavamurthy Anil S Date: Wed, 11 Jan 2006 12:17:42 -0800 Subject: [PATCH] kprobes: fix race in recovery of reentrant probe There is a window where a probe gets removed right after the probe is hit on some different cpu. In this case probe handlers can't find a matching probe instance related to break address. In this case we need to read the original instruction at break address to see if that is not a break/int3 instruction and recover safely. Previous code had a bug where we were not checking for the above race in case of reentrant probes and the below patch fixes this race. Tested on IA64, Powerpc, x86_64. Signed-off-by: Anil S Keshavamurthy Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/i386/kernel/kprobes.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'arch/i386') diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c index 2f372dbd34fd..6483eeb1a4e8 100644 --- a/arch/i386/kernel/kprobes.c +++ b/arch/i386/kernel/kprobes.c @@ -188,6 +188,19 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) kcb->kprobe_status = KPROBE_REENTER; return 1; } else { + if (regs->eflags & VM_MASK) { + /* We are in virtual-8086 mode. Return 0 */ + goto no_kprobe; + } + if (*addr != BREAKPOINT_INSTRUCTION) { + /* The breakpoint instruction was removed by + * another cpu right after we hit, no further + * handling of this interrupt is appropriate + */ + regs->eip -= sizeof(kprobe_opcode_t); + ret = 1; + goto no_kprobe; + } p = __get_cpu_var(current_kprobe); if (p->break_handler && p->break_handler(p, regs)) { goto ss_probe; -- cgit v1.2.3