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| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2017-04-17 08:44:00 -0500 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-04-18 10:30:23 +0200 |
| commit | e335bb51cc15e80ac180701a0d335ef1c050828e (patch) | |
| tree | 2e4543538bfc26e5b1867c0bc82b92f5f10cc0fd | |
| parent | f26dee15103f4040bfe21c910131db0cfe6624fc (diff) | |
| download | linux-e335bb51cc15e80ac180701a0d335ef1c050828e.tar.gz linux-e335bb51cc15e80ac180701a0d335ef1c050828e.tar.bz2 linux-e335bb51cc15e80ac180701a0d335ef1c050828e.zip | |
x86/unwind: Ensure stack pointer is aligned
With frame pointers disabled, on some older versions of GCC (like
4.8.3), it's possible for the stack pointer to get aligned at a
half-word boundary:
00000000000004d0 <fib_table_lookup>:
4d0: 41 57 push %r15
4d2: 41 56 push %r14
4d4: 41 55 push %r13
4d6: 41 54 push %r12
4d8: 55 push %rbp
4d9: 53 push %rbx
4da: 48 83 ec 24 sub $0x24,%rsp
In such a case, the unwinder ends up reading the entire stack at the
wrong alignment. Then the last read goes past the end of the stack,
hitting the stack guard page:
BUG: stack guard page was hit at ffffc900217c4000 (stack is ffffc900217c0000..ffffc900217c3fff)
kernel stack overflow (page fault): 0000 [#1] SMP
...
Fix it by ensuring the stack pointer is properly aligned before
unwinding.
Reported-by: Jirka Hladky <jhladky@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: 7c7900f89770 ("x86/unwind: Add new unwind interface and implementations")
Link: http://lkml.kernel.org/r/cff33847cc9b02fa548625aa23268ac574460d8d.1492436590.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | arch/x86/kernel/dumpstack.c | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/unwind_guess.c | 4 |
2 files changed, 3 insertions, 3 deletions
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index 924f45ea4382..dbce3cca94cb 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -77,7 +77,7 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs, * - softirq stack * - hardirq stack */ - for (regs = NULL; stack; stack = stack_info.next_sp) { + for (regs = NULL; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) { const char *stack_name; /* diff --git a/arch/x86/kernel/unwind_guess.c b/arch/x86/kernel/unwind_guess.c index 22881ddcbb9f..039f36738e49 100644 --- a/arch/x86/kernel/unwind_guess.c +++ b/arch/x86/kernel/unwind_guess.c @@ -34,7 +34,7 @@ bool unwind_next_frame(struct unwind_state *state) return true; } - state->sp = info->next_sp; + state->sp = PTR_ALIGN(info->next_sp, sizeof(long)); } while (!get_stack_info(state->sp, state->task, info, &state->stack_mask)); @@ -49,7 +49,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, memset(state, 0, sizeof(*state)); state->task = task; - state->sp = first_frame; + state->sp = PTR_ALIGN(first_frame, sizeof(long)); get_stack_info(first_frame, state->task, &state->stack_info, &state->stack_mask); |