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authorOleg Nesterov <oleg@redhat.com>2015-07-21 15:40:21 +0200
committerIngo Molnar <mingo@kernel.org>2015-07-31 10:38:05 +0200
commit5eeb50de42fd3251845d03c556db012267c72b3f (patch)
tree4deccaa1d1835099c6ee9945166f316f1bf003bc /kernel/events
parent7b868e4802a86d867aad1be0471b5767d9c20e10 (diff)
downloadlinux-5eeb50de42fd3251845d03c556db012267c72b3f.tar.bz2
uprobes: Change handle_trampoline() to flush the frames invalidated by longjmp()
Test-case: #include <stdio.h> #include <setjmp.h> jmp_buf jmp; void func_2(void) { longjmp(jmp, 1); } void func_1(void) { if (setjmp(jmp)) return; func_2(); printf("ERR!! I am running on the caller's stack\n"); } int main(void) { func_1(); return 0; } fails if you probe func_1() and func_2() because handle_trampoline() assumes that the probed function should must return and hit the bp installed be prepare_uretprobe(). But in this case func_2() does not return, so when func_1() returns the kernel uses the no longer valid return_instance of func_2(). Change handle_trampoline() to unwind ->return_instances until we know that the next chain is alive or NULL, this ensures that the current chain is the last we need to report and free. Alternatively, every return_instance could use unique trampoline_vaddr, in this case we could use it as a key. And this could solve the problem with sigaltstack() automatically. But this approach needs more changes, and it puts the "hard" limit on MAX_URETPROBE_DEPTH. Plus it can not solve another problem partially fixed by the next patch. Note: this change has no effect on !x86, the arch-agnostic version of arch_uretprobe_is_alive() just returns "true". TODO: as documented by the previous change, arch_uretprobe_is_alive() can be fooled by sigaltstack/etc. Tested-by: Pratyush Anand <panand@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Anton Arapov <arapov@gmail.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150721134021.GA4773@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/uprobes.c29
1 files changed, 18 insertions, 11 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index c5f316e06dc0..93d939c80cd9 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1774,6 +1774,7 @@ static void handle_trampoline(struct pt_regs *regs)
{
struct uprobe_task *utask;
struct return_instance *ri, *next;
+ bool valid;
utask = current->utask;
if (!utask)
@@ -1783,18 +1784,24 @@ static void handle_trampoline(struct pt_regs *regs)
if (!ri)
goto sigill;
- next = find_next_ret_chain(ri);
- /*
- * TODO: we should throw out return_instance's invalidated by
- * longjmp(), currently we assume that the probed function always
- * returns.
- */
- instruction_pointer_set(regs, ri->orig_ret_vaddr);
do {
- handle_uretprobe_chain(ri, regs);
- ri = free_ret_instance(ri);
- utask->depth--;
- } while (ri != next);
+ /*
+ * We should throw out the frames invalidated by longjmp().
+ * If this chain is valid, then the next one should be alive
+ * or NULL; the latter case means that nobody but ri->func
+ * could hit this trampoline on return. TODO: sigaltstack().
+ */
+ next = find_next_ret_chain(ri);
+ valid = !next || arch_uretprobe_is_alive(next, regs);
+
+ instruction_pointer_set(regs, ri->orig_ret_vaddr);
+ do {
+ if (valid)
+ handle_uretprobe_chain(ri, regs);
+ ri = free_ret_instance(ri);
+ utask->depth--;
+ } while (ri != next);
+ } while (!valid);
utask->return_instances = ri;
return;