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| author | André Rösti <an.roesti@gmail.com> | 2024-03-11 21:17:04 +0000 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2024-03-12 13:23:32 +0100 |
| commit | fb13b11d53875e28e7fbf0c26b288e4ea676aa9f (patch) | |
| tree | 05733ac23e08a6a8a9b3bc2283912a28b7a1afbf | |
| parent | e8f897f4afef0031fe618a8e94127a0934896aba (diff) | |
| download | lwn-fb13b11d53875e28e7fbf0c26b288e4ea676aa9f.tar.gz lwn-fb13b11d53875e28e7fbf0c26b288e4ea676aa9f.zip | |
entry: Respect changes to system call number by trace_sys_enter()
When a probe is registered at the trace_sys_enter() tracepoint, and that
probe changes the system call number, the old system call still gets
executed. This worked correctly until commit b6ec41346103 ("core/entry:
Report syscall correctly for trace and audit"), which removed the
re-evaluation of the syscall number after the trace point.
Restore the original semantics by re-evaluating the system call number
after trace_sys_enter().
The performance impact of this re-evaluation is minimal because it only
takes place when a trace point is active, and compared to the actual trace
point overhead the read from a cache hot variable is negligible.
Fixes: b6ec41346103 ("core/entry: Report syscall correctly for trace and audit")
Signed-off-by: André Rösti <an.roesti@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240311211704.7262-1-an.roesti@gmail.com
| -rw-r--r-- | kernel/entry/common.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 88cb3c88aaa5..90843cc38588 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -57,8 +57,14 @@ long syscall_trace_enter(struct pt_regs *regs, long syscall, /* Either of the above might have changed the syscall number */ syscall = syscall_get_nr(current, regs); - if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT)) + if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT)) { trace_sys_enter(regs, syscall); + /* + * Probes or BPF hooks in the tracepoint may have changed the + * system call number as well. + */ + syscall = syscall_get_nr(current, regs); + } syscall_enter_audit(regs, syscall); |