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7fbe6ac024
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: 7c7900f897 ("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>
61 lines
1.5 KiB
C
61 lines
1.5 KiB
C
#include <linux/sched.h>
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#include <linux/ftrace.h>
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#include <asm/ptrace.h>
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#include <asm/bitops.h>
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#include <asm/stacktrace.h>
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#include <asm/unwind.h>
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unsigned long unwind_get_return_address(struct unwind_state *state)
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{
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if (unwind_done(state))
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return 0;
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return ftrace_graph_ret_addr(state->task, &state->graph_idx,
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*state->sp, state->sp);
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}
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EXPORT_SYMBOL_GPL(unwind_get_return_address);
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bool unwind_next_frame(struct unwind_state *state)
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{
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struct stack_info *info = &state->stack_info;
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if (unwind_done(state))
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return false;
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do {
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for (state->sp++; state->sp < info->end; state->sp++)
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if (__kernel_text_address(*state->sp))
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return true;
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state->sp = info->next_sp;
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} while (!get_stack_info(state->sp, state->task, info,
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&state->stack_mask));
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return false;
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}
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EXPORT_SYMBOL_GPL(unwind_next_frame);
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void __unwind_start(struct unwind_state *state, struct task_struct *task,
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struct pt_regs *regs, unsigned long *first_frame)
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{
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memset(state, 0, sizeof(*state));
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state->task = task;
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state->sp = first_frame;
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get_stack_info(first_frame, state->task, &state->stack_info,
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&state->stack_mask);
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/*
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* The caller can provide the address of the first frame directly
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* (first_frame) or indirectly (regs->sp) to indicate which stack frame
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* to start unwinding at. Skip ahead until we reach it.
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*/
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if (!unwind_done(state) &&
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(!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
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!__kernel_text_address(*first_frame)))
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unwind_next_frame(state);
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}
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EXPORT_SYMBOL_GPL(__unwind_start);
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