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authorJosh Poimboeuf <jpoimboe@redhat.com>2016-10-24 15:31:27 +0200
committerIngo Molnar <mingo@kernel.org>2016-10-25 11:36:43 +0200
commit7fbe6ac02485504b964b283aca62b36b4313ca79 (patch)
treebd33b5c4be28465b10b83cf7d1c2d08a52e5f5a0 /Makefile
parentMerge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert... (diff)
downloadlinux-7fbe6ac02485504b964b283aca62b36b4313ca79.tar.xz
linux-7fbe6ac02485504b964b283aca62b36b4313ca79.zip
x86/unwind: Fix empty stack dereference in guess unwinder
Vince Waver reported the following bug: WARNING: CPU: 0 PID: 21338 at arch/x86/mm/fault.c:435 vmalloc_fault+0x58/0x1f0 CPU: 0 PID: 21338 Comm: perf_fuzzer Not tainted 4.8.0+ #37 Hardware name: Hewlett-Packard HP Compaq Pro 6305 SFF/1850, BIOS K06 v02.57 08/16/2013 Call Trace: <NMI> ? dump_stack+0x46/0x59 ? __warn+0xd5/0xee ? vmalloc_fault+0x58/0x1f0 ? __do_page_fault+0x6d/0x48e ? perf_log_throttle+0xa4/0xf4 ? trace_page_fault+0x22/0x30 ? __unwind_start+0x28/0x42 ? perf_callchain_kernel+0x75/0xac ? get_perf_callchain+0x13a/0x1f0 ? perf_callchain+0x6a/0x6c ? perf_prepare_sample+0x71/0x2eb ? perf_event_output_forward+0x1a/0x54 ? __default_send_IPI_shortcut+0x10/0x2d ? __perf_event_overflow+0xfb/0x167 ? x86_pmu_handle_irq+0x113/0x150 ? native_read_msr+0x6/0x34 ? perf_event_nmi_handler+0x22/0x39 ? perf_ibs_nmi_handler+0x4a/0x51 ? perf_event_nmi_handler+0x22/0x39 ? nmi_handle+0x4d/0xf0 ? perf_ibs_handle_irq+0x3d1/0x3d1 ? default_do_nmi+0x3c/0xd5 ? do_nmi+0x92/0x102 ? end_repeat_nmi+0x1a/0x1e ? entry_SYSCALL_64_after_swapgs+0x12/0x4a ? entry_SYSCALL_64_after_swapgs+0x12/0x4a ? entry_SYSCALL_64_after_swapgs+0x12/0x4a <EOE> ^A4---[ end trace 632723104d47d31a ]--- BUG: stack guard page was hit at ffffc90008500000 (stack is ffffc900084fc000..ffffc900084fffff) kernel stack overflow (page fault): 0000 [#1] SMP ... The NMI hit in the entry code right after setting up the stack pointer from 'cpu_current_top_of_stack', so the kernel stack was empty. The 'guess' version of __unwind_start() attempted to dereference the "top of stack" pointer, which is not actually *on* the stack. Add a check in the guess unwinder to deal with an empty stack. (The frame pointer unwinder already has such a check.) Reported-by: Vince Weaver <vincent.weaver@maine.edu> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 7c7900f89770 ("x86/unwind: Add new unwind interface and implementations") Link: http://lkml.kernel.org/r/20161024133127.e5evgeebdbohnmpb@treble Signed-off-by: Ingo Molnar <mingo@kernel.org>
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