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Johannes Weiner authored
commit ae31fe51 upstream. The following commit: 75925e1a ("perf/x86: Optimize stack walk user accesses") ... switched from copy_from_user_nmi() to __copy_from_user_nmi() with a manual access_ok() check. Unfortunately, copy_from_user_nmi() does an explicit check against TASK_SIZE, whereas the access_ok() uses whatever the current address limit of the task is. We are getting NMIs when __probe_kernel_read() has switched to KERNEL_DS, and then see vmalloc faults when we access what looks like pointers into vmalloc space: [] WARNING: CPU: 3 PID: 3685731 at arch/x86/mm/fault.c:435 vmalloc_fault+0x289/0x290 [] CPU: 3 PID: 3685731 Comm: sh Tainted: G W 4.6.0-5_fbk1_223_gdbf0f40 #1 [] Call Trace: [] <NMI> [<ffffffff814717d1>] dump_stack+0x4d/0x6c [] [<ffffffff81076e43>] __warn+0xd3/0xf0 [] [<ffffffff81076f2d>] warn_slowpath_null+0x1d/0x20 [] [<ffffffff8104a899>] vmalloc_fault+0x289/0x290 [] [<ffffffff8104b5a0>] __do_page_fault+0x330/0x490 [] [<ffffffff8104b70c>] do_page_fault+0xc/0x10 [] [<ffffffff81794e82>] page_fault+0x22/0x30 [] [<ffffffff81006280>] ? perf_callchain_user+0x100/0x2a0 [] [<ffffffff8115124f>] get_perf_callchain+0x17f/0x190 [] [<ffffffff811512c7>] perf_callchain+0x67/0x80 [] [<ffffffff8114e750>] perf_prepare_sample+0x2a0/0x370 [] [<ffffffff8114e840>] perf_event_output+0x20/0x60 [] [<ffffffff8114aee7>] ? perf_event_update_userpage+0xc7/0x130 [] [<ffffffff8114ea01>] __perf_event_overflow+0x181/0x1d0 [] [<ffffffff8114f484>] perf_event_overflow+0x14/0x20 [] [<ffffffff8100a6e3>] intel_pmu_handle_irq+0x1d3/0x490 [] [<ffffffff8147daf7>] ? copy_user_enhanced_fast_string+0x7/0x10 [] [<ffffffff81197191>] ? vunmap_page_range+0x1a1/0x2f0 [] [<ffffffff811972f1>] ? unmap_kernel_range_noflush+0x11/0x20 [] [<ffffffff814f2056>] ? ghes_copy_tofrom_phys+0x116/0x1f0 [] [<ffffffff81040d1d>] ? x2apic_send_IPI_self+0x1d/0x20 [] [<ffffffff8100411d>] perf_event_nmi_handler+0x2d/0x50 [] [<ffffffff8101ea31>] nmi_handle+0x61/0x110 [] [<ffffffff8101ef94>] default_do_nmi+0x44/0x110 [] [<ffffffff8101f13b>] do_nmi+0xdb/0x150 [] [<ffffffff81795187>] end_repeat_nmi+0x1a/0x1e [] [<ffffffff8147daf7>] ? copy_user_enhanced_fast_string+0x7/0x10 [] [<ffffffff8147daf7>] ? copy_user_enhanced_fast_string+0x7/0x10 [] [<ffffffff8147daf7>] ? copy_user_enhanced_fast_string+0x7/0x10 [] <<EOE>> <IRQ> [<ffffffff8115d05e>] ? __probe_kernel_read+0x3e/0xa0 Fix this by moving the valid_user_frame() check to before the uaccess that loads the return address and the pointer to the next frame. Signed-off-by:
Johannes Weiner <hannes@cmpxchg.org> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: linux-kernel@vger.kernel.org Fixes: 75925e1a ("perf/x86: Optimize stack walk user accesses") Signed-off-by:
Ingo Molnar <mingo@kernel.org> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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