6.6-stable review patch. If anyone has any objections, please let me know.
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From: André Rösti an.roesti@gmail.com
[ Upstream commit fb13b11d53875e28e7fbf0c26b288e4ea676aa9f ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/entry/common.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/kernel/entry/common.c b/kernel/entry/common.c index d7ee4bc3f2ba3..5ff4f1cd36445 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -77,8 +77,14 @@ static 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);