From ae31fe51a3cceaa0cabdb3058f69669ecb47f12e Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Tue, 22 Nov 2016 10:57:42 +0100 Subject: [PATCH] perf/x86: Restore TASK_SIZE check on frame pointer The following commit: 75925e1ad7f5 ("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: [] [] dump_stack+0x4d/0x6c [] [] __warn+0xd3/0xf0 [] [] warn_slowpath_null+0x1d/0x20 [] [] vmalloc_fault+0x289/0x290 [] [] __do_page_fault+0x330/0x490 [] [] do_page_fault+0xc/0x10 [] [] page_fault+0x22/0x30 [] [] ? perf_callchain_user+0x100/0x2a0 [] [] get_perf_callchain+0x17f/0x190 [] [] perf_callchain+0x67/0x80 [] [] perf_prepare_sample+0x2a0/0x370 [] [] perf_event_output+0x20/0x60 [] [] ? perf_event_update_userpage+0xc7/0x130 [] [] __perf_event_overflow+0x181/0x1d0 [] [] perf_event_overflow+0x14/0x20 [] [] intel_pmu_handle_irq+0x1d3/0x490 [] [] ? copy_user_enhanced_fast_string+0x7/0x10 [] [] ? vunmap_page_range+0x1a1/0x2f0 [] [] ? unmap_kernel_range_noflush+0x11/0x20 [] [] ? ghes_copy_tofrom_phys+0x116/0x1f0 [] [] ? x2apic_send_IPI_self+0x1d/0x20 [] [] perf_event_nmi_handler+0x2d/0x50 [] [] nmi_handle+0x61/0x110 [] [] default_do_nmi+0x44/0x110 [] [] do_nmi+0xdb/0x150 [] [] end_repeat_nmi+0x1a/0x1e [] [] ? copy_user_enhanced_fast_string+0x7/0x10 [] [] ? copy_user_enhanced_fast_string+0x7/0x10 [] [] ? copy_user_enhanced_fast_string+0x7/0x10 [] <> [] ? __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 Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Cc: linux-kernel@vger.kernel.org Fixes: 75925e1ad7f5 ("perf/x86: Optimize stack walk user accesses") Signed-off-by: Ingo Molnar --- arch/x86/events/core.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index d31735f37ed7..9d4bf3ab049e 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -2352,7 +2352,7 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry_ctx *ent frame.next_frame = 0; frame.return_address = 0; - if (!access_ok(VERIFY_READ, fp, 8)) + if (!valid_user_frame(fp, sizeof(frame))) break; bytes = __copy_from_user_nmi(&frame.next_frame, fp, 4); @@ -2362,9 +2362,6 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry_ctx *ent if (bytes != 0) break; - if (!valid_user_frame(fp, sizeof(frame))) - break; - perf_callchain_store(entry, cs_base + frame.return_address); fp = compat_ptr(ss_base + frame.next_frame); } @@ -2413,7 +2410,7 @@ perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs frame.next_frame = NULL; frame.return_address = 0; - if (!access_ok(VERIFY_READ, fp, sizeof(*fp) * 2)) + if (!valid_user_frame(fp, sizeof(frame))) break; bytes = __copy_from_user_nmi(&frame.next_frame, fp, sizeof(*fp)); @@ -2423,9 +2420,6 @@ perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs if (bytes != 0) break; - if (!valid_user_frame(fp, sizeof(frame))) - break; - perf_callchain_store(entry, frame.return_address); fp = (void __user *)frame.next_frame; }