summaryrefslogtreecommitdiffstats
path: root/arch/x86/include/asm
diff options
context:
space:
mode:
authorJann Horn <jannh@google.com>2019-03-01 04:12:00 +0100
committerThomas Gleixner <tglx@linutronix.de>2019-03-06 23:03:26 +0100
commitf4f34e1b82eb4219d8eaa1c7e2e17ca219a6a2b5 (patch)
tree39e828e4a85f6b3f57c0f7b77e9d36924766ed1d /arch/x86/include/asm
parentf76a16adc485699f95bb71fce114f97c832fe664 (diff)
downloadlinux-0-day-f4f34e1b82eb4219d8eaa1c7e2e17ca219a6a2b5.tar.gz
linux-0-day-f4f34e1b82eb4219d8eaa1c7e2e17ca219a6a2b5.tar.xz
x86/unwind: Handle NULL pointer calls better in frame unwinder
When the frame unwinder is invoked for an oops caused by a call to NULL, it currently skips the parent function because BP still points to the parent's stack frame; the (nonexistent) current function only has the first half of a stack frame, and BP doesn't point to it yet. Add a special case for IP==0 that calculates a fake BP from SP, then uses the real BP for the next frame. Note that this handles first_frame specially: Return information about the parent function as long as the saved IP is >=first_frame, even if the fake BP points below it. With an artificially-added NULL call in prctl_set_seccomp(), before this patch, the trace is: Call Trace: ? prctl_set_seccomp+0x3a/0x50 __x64_sys_prctl+0x457/0x6f0 ? __ia32_sys_prctl+0x750/0x750 do_syscall_64+0x72/0x160 entry_SYSCALL_64_after_hwframe+0x44/0xa9 After this patch, the trace is: Call Trace: prctl_set_seccomp+0x3a/0x50 __x64_sys_prctl+0x457/0x6f0 ? __ia32_sys_prctl+0x750/0x750 do_syscall_64+0x72/0x160 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Michal Marek <michal.lkml@markovi.net> Cc: linux-kbuild@vger.kernel.org Link: https://lkml.kernel.org/r/20190301031201.7416-1-jannh@google.com
Diffstat (limited to 'arch/x86/include/asm')
-rw-r--r--arch/x86/include/asm/unwind.h6
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
index 1f86e1b0a5cd..499578f7e6d7 100644
--- a/arch/x86/include/asm/unwind.h
+++ b/arch/x86/include/asm/unwind.h
@@ -23,6 +23,12 @@ struct unwind_state {
#elif defined(CONFIG_UNWINDER_FRAME_POINTER)
bool got_irq;
unsigned long *bp, *orig_sp, ip;
+ /*
+ * If non-NULL: The current frame is incomplete and doesn't contain a
+ * valid BP. When looking for the next frame, use this instead of the
+ * non-existent saved BP.
+ */
+ unsigned long *next_bp;
struct pt_regs *regs;
#else
unsigned long *sp;