• Jann Horn's avatar
    x86/unwind: Add hardcoded ORC entry for NULL · 5befc25f
    Jann Horn authored
    commit ac5ceccce5501e43d217c596e4ee859f2a3fef79 upstream.
    
    When the ORC unwinder is invoked for an oops caused by IP==0,
    it currently has no idea what to do because there is no debug information
    for the stack frame of NULL.
    
    But if RIP is NULL, it is very likely that the last successfully executed
    instruction was an indirect CALL/JMP, and it is possible to unwind out in
    the same way as for the first instruction of a normal function. Hardcode
    a corresponding ORC entry.
    
    With an artificially-added NULL call in prctl_set_seccomp(), before this
    patch, the trace is:
    
    Call Trace:
     ? __x64_sys_prctl+0x402/0x680
     ? __ia32_sys_prctl+0x6e0/0x6e0
     ? __do_page_fault+0x457/0x620
     ? do_syscall_64+0x6d/0x160
     ? entry_SYSCALL_64_after_hwframe+0x44/0xa9
    
    After this patch, the trace looks like this:
    
    Call Trace:
     __x64_sys_prctl+0x402/0x680
     ? __ia32_sys_prctl+0x6e0/0x6e0
     ? __do_page_fault+0x457/0x620
     do_syscall_64+0x6d/0x160
     entry_SYSCALL_64_after_hwframe+0x44/0xa9
    
    prctl_set_seccomp() still doesn't show up in the trace because for some
    reason, tail call optimization is only disabled in builds that use the
    frame pointer unwinder.
    Signed-off-by: default avatarJann Horn <jannh@google.com>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Acked-by: default avatarJosh 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/20190301031201.7416-2-jannh@google.comSigned-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    5befc25f
Name
Last commit
Last update
..
alpha Loading commit data...
arc Loading commit data...
arm Loading commit data...
arm64 Loading commit data...
blackfin Loading commit data...
c6x Loading commit data...
cris Loading commit data...
frv Loading commit data...
h8300 Loading commit data...
hexagon Loading commit data...
ia64 Loading commit data...
m32r Loading commit data...
m68k Loading commit data...
metag Loading commit data...
microblaze Loading commit data...
mips Loading commit data...
mn10300 Loading commit data...
nios2 Loading commit data...
openrisc Loading commit data...
parisc Loading commit data...
powerpc Loading commit data...
s390 Loading commit data...
score Loading commit data...
sh Loading commit data...
sparc Loading commit data...
tile Loading commit data...
um Loading commit data...
unicore32 Loading commit data...
x86 Loading commit data...
xtensa Loading commit data...
.gitignore Loading commit data...
Kconfig Loading commit data...