Commits
Josh Poimboeuf committed e335bb51cc1
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>