| Message ID | 20211113194117.22680-1-svens@stackframe.org (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
| Series | [v2] parisc/entry: fix trace test in syscall exit path | expand |
diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S index 57944d6f9ebb..88c188a965d8 100644 --- a/arch/parisc/kernel/entry.S +++ b/arch/parisc/kernel/entry.S @@ -1805,7 +1805,7 @@ syscall_restore: /* Are we being ptraced? */ LDREG TASK_TI_FLAGS(%r1),%r19 - ldi _TIF_SYSCALL_TRACE_MASK,%r2 + ldi _TIF_SINGLESTEP|_TIF_BLOCKSTEP,%r2 and,COND(=) %r19,%r2,%r0 b,n syscall_restore_rfi
commit 8779e05ba8aa ("parisc: Fix ptrace check on syscall return") fixed testing of TI_FLAGS. This uncovered a bug in the test mask. syscall_restore_rfi is only used when the kernel needs to exit to usespace with single or block stepping and the recovery counter enabled. The test however used _TIF_SYSCALL_TRACE_MASK, which includes a lot of bits that shouldn't be tested here. Fix this by using TIF_SINGLESTEP and TIF_BLOCKSTEP directly. I encountered this bug by enabling syscall tracepoints. Both in qemu and on real hardware. As soon as i enabled the tracepoint (sys_exit_read, but i guess it doesn't really matter which one), i got random page faults in userspace almost immediately. Signed-off-by: Sven Schnelle <svens@stackframe.org> --- arch/parisc/kernel/entry.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)