From 256aae5eac6d328067d1a986a7c5df6f19bdc8b4 Mon Sep 17 00:00:00 2001 From: Wang Nan Date: Mon, 28 Jul 2014 20:20:19 +0800 Subject: [PATCH 1/2] kprobes/x86: Free 'optinsn' cache when range check fails This patch frees the 'optinsn' slot when we get a range check error, to prevent memory leaks. Before this patch, cache entry in kprobe_insn_cache() won't be freed if kprobe optimizing fails due to range check failure. Signed-off-by: Wang Nan Acked-by: Masami Hiramatsu Cc: Pei Feiyue Link: http://lkml.kernel.org/r/1406550019-70935-1-git-send-email-wangnan0@huawei.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/kprobes/opt.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c index f304773285ae..f1314d0bcf0a 100644 --- a/arch/x86/kernel/kprobes/opt.c +++ b/arch/x86/kernel/kprobes/opt.c @@ -338,8 +338,10 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op) * a relative jump. */ rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE; - if (abs(rel) > 0x7fffffff) + if (abs(rel) > 0x7fffffff) { + __arch_remove_optimized_kprobe(op, 0); return -ERANGE; + } buf = (u8 *)op->optinsn.insn; From 3577af70a2ce4853d58e57d832e687d739281479 Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Tue, 2 Sep 2014 15:27:20 -0700 Subject: [PATCH 2/2] perf: Fix a race condition in perf_remove_from_context() We saw a kernel soft lockup in perf_remove_from_context(), it looks like the `perf` process, when exiting, could not go out of the retry loop. Meanwhile, the target process was forking a child. So either the target process should execute the smp function call to deactive the event (if it was running) or it should do a context switch which deactives the event. It seems we optimize out a context switch in perf_event_context_sched_out(), and what's more important, we still test an obsolete task pointer when retrying, so no one actually would deactive that event in this situation. Fix it directly by reloading the task pointer in perf_remove_from_context(). This should cure the above soft lockup. Signed-off-by: Cong Wang Signed-off-by: Cong Wang Signed-off-by: Peter Zijlstra Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: Linus Torvalds Cc: Link: http://lkml.kernel.org/r/1409696840-843-1-git-send-email-xiyou.wangcong@gmail.com Signed-off-by: Ingo Molnar --- kernel/events/core.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/kernel/events/core.c b/kernel/events/core.c index f9c1ed002dbc..d640a8b4dcbc 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -1524,6 +1524,11 @@ static void perf_remove_from_context(struct perf_event *event, bool detach_group */ if (ctx->is_active) { raw_spin_unlock_irq(&ctx->lock); + /* + * Reload the task pointer, it might have been changed by + * a concurrent perf_event_context_sched_out(). + */ + task = ctx->task; goto retry; } @@ -1967,6 +1972,11 @@ perf_install_in_context(struct perf_event_context *ctx, */ if (ctx->is_active) { raw_spin_unlock_irq(&ctx->lock); + /* + * Reload the task pointer, it might have been changed by + * a concurrent perf_event_context_sched_out(). + */ + task = ctx->task; goto retry; }