diff options
| author |   Andy Lutomirski <luto@kernel.org> | 2019-11-20 12:59:13 -0800 |
|---|---|---|
| committer |   Peter Zijlstra <peterz@infradead.org> | 2019-11-21 21:55:51 +0100 |
| commit | 8caa016bfc129f2c925d52da43022171d1d1de91 (patch) | |
| tree | 6d07aa64ec511f3175cbeb31ad170fcb96e478bc /tools/testing/selftests | |
| parent | x86/entry/32: Fix NMI vs ESPFIX (diff) | |
| download | wireguard-linux-8caa016bfc129f2c925d52da43022171d1d1de91.tar.xz wireguard-linux-8caa016bfc129f2c925d52da43022171d1d1de91.zip | |
selftests/x86/mov_ss_trap: Fix the SYSENTER test
For reasons that I haven't quite fully diagnosed, running
mov_ss_trap_32 on a 32-bit kernel results in an infinite loop in
userspace. This appears to be because the hacky SYSENTER test
doesn't segfault as desired; instead it corrupts the program state
such that it infinite loops.
Fix it by explicitly clearing EBP before doing SYSENTER. This will
give a more reliable segfault.
Fixes: 59c2a7226fc5 ("x86/selftests: Add mov_to_ss test")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@kernel.org
Diffstat (limited to 'tools/testing/selftests')
| -rw-r--r-- | tools/testing/selftests/x86/mov_ss_trap.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/tools/testing/selftests/x86/mov_ss_trap.c b/tools/testing/selftests/x86/mov_ss_trap.c index 3c3a022654f3..6da0ac3f0135 100644 --- a/tools/testing/selftests/x86/mov_ss_trap.c +++ b/tools/testing/selftests/x86/mov_ss_trap.c @@ -257,7 +257,8 @@ int main() err(1, "sigaltstack"); sethandler(SIGSEGV, handle_and_longjmp, SA_RESETHAND | SA_ONSTACK); nr = SYS_getpid; - asm volatile ("mov %[ss], %%ss; SYSENTER" : "+a" (nr) + /* Clear EBP first to make sure we segfault cleanly. */ + asm volatile ("xorl %%ebp, %%ebp; mov %[ss], %%ss; SYSENTER" : "+a" (nr) : [ss] "m" (ss) : "flags", "rcx" #ifdef __x86_64__ , "r11" |