From: Keshavamurthy Anil S Date: Wed, 11 Jan 2006 20:17:42 +0000 (-0800) Subject: [PATCH] kprobes: fix race in recovery of reentrant probe X-Git-Tag: v2.6.16-rc1~398 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=eb3a72921c8276bf2cd028a458bb83435f16c91c;p=linux-2.6 [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 --- diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c index 2f372dbd34..6483eeb1a4 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; diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c index 4de7f67590..346fedf9ea 100644 --- a/arch/ia64/kernel/kprobes.c +++ b/arch/ia64/kernel/kprobes.c @@ -638,6 +638,13 @@ static int __kprobes pre_kprobes_handler(struct die_args *args) if (p->break_handler && p->break_handler(p, regs)) { goto ss_probe; } + } else if (!is_ia64_break_inst(regs)) { + /* The breakpoint instruction was removed by + * another cpu right after we hit, no further + * handling of this interrupt is appropriate + */ + ret = 1; + goto no_kprobe; } else { /* Not our break */ goto no_kprobe; diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c index 27b0c40601..cfab48566d 100644 --- a/arch/powerpc/kernel/kprobes.c +++ b/arch/powerpc/kernel/kprobes.c @@ -179,6 +179,18 @@ static inline int kprobe_handler(struct pt_regs *regs) kcb->kprobe_status = KPROBE_REENTER; return 1; } else { + if (*addr != BREAKPOINT_INSTRUCTION) { + /* If trap variant, then it belongs not to us */ + kprobe_opcode_t cur_insn = *addr; + if (is_trap(cur_insn)) + goto no_kprobe; + /* The breakpoint instruction was removed by + * another cpu right after we hit, no further + * handling of this interrupt is appropriate + */ + ret = 1; + goto no_kprobe; + } p = __get_cpu_var(current_kprobe); if (p->break_handler && p->break_handler(p, regs)) { goto ss_probe; diff --git a/arch/sparc64/kernel/kprobes.c b/arch/sparc64/kernel/kprobes.c index ff5e9d5cad..b9a9ce70e5 100644 --- a/arch/sparc64/kernel/kprobes.c +++ b/arch/sparc64/kernel/kprobes.c @@ -135,6 +135,14 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) prepare_singlestep(p, regs, kcb); return 1; } else { + if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) { + /* The breakpoint instruction was removed by + * another cpu right after we hit, no further + * handling of this interrupt is appropriate + */ + ret = 1; + goto no_kprobe; + } p = __get_cpu_var(current_kprobe); if (p->break_handler && p->break_handler(p, regs)) goto ss_probe; diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c index b7dc1f816d..8b866a8572 100644 --- a/arch/x86_64/kernel/kprobes.c +++ b/arch/x86_64/kernel/kprobes.c @@ -334,6 +334,15 @@ int __kprobes kprobe_handler(struct pt_regs *regs) return 1; } } else { + 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->rip = (unsigned long)addr; + ret = 1; + goto no_kprobe; + } p = __get_cpu_var(current_kprobe); if (p->break_handler && p->break_handler(p, regs)) { goto ss_probe;