redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

arm64: Fix PTRACE_SYSEMU semantics 

commit 1cf6022bd9 upstream.

Quoth the man page:
```
       If the tracee was restarted by PTRACE_SYSCALL or PTRACE_SYSEMU, the
       tracee enters syscall-enter-stop just prior to entering any system
       call (which will not be executed if the restart was using
       PTRACE_SYSEMU, regardless of any change made to registers at this
       point or how the tracee is restarted after this stop).
```

The parenthetical comment is currently true on x86 and powerpc,
but not currently true on arm64. arm64 re-checks the _TIF_SYSCALL_EMU
flag after the syscall entry ptrace stop. However, at this point,
it reflects which method was used to re-start the syscall
at the entry stop, rather than the method that was used to reach it.
Fix that by recording the original flag before performing the ptrace
stop, bringing the behavior in line with documentation and x86/powerpc.

Fixes: f086f67485 ("arm64: ptrace: add support for syscall emulation")
Cc: <stable@vger.kernel.org> # 5.3.x-
Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Acked-by: Will Deacon <will@kernel.org>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Bin Lu <Bin.Lu@arm.com>
[catalin.marinas@arm.com: moved 'flags' bit masking]
[catalin.marinas@arm.com: changed 'flags' type to unsigned long]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
Keno Fischer 2020-05-15 18:22:53 -04:00 committed by Greg Kroah-Hartman
parent 96e56055a2
commit 53683907ef
1 changed files with 4 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
arch/arm64/kernel/ptrace.c
View File

@ -1829,10 +1829,11 @@ static void tracehook_report_syscall(struct pt_regs *regs,
int syscall_trace_enter(struct pt_regs *regs)
{
if (test_thread_flag(TIF_SYSCALL_TRACE) ||
test_thread_flag(TIF_SYSCALL_EMU)) {
unsigned long flags = READ_ONCE(current_thread_info()->flags);
if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {
tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
if (!in_syscall(regs) || test_thread_flag(TIF_SYSCALL_EMU))
if (!in_syscall(regs) || (flags & _TIF_SYSCALL_EMU))
return -1;
}