diff options
| author | Marco Elver <elver@google.com> | 2024-11-08 12:34:24 +0100 |
|---|---|---|
| committer | Kees Cook <kees@kernel.org> | 2024-12-22 20:28:11 -0800 |
| commit | c38904ebb74b455a44e3b9a679aef320361654ae (patch) | |
| tree | ddf8d449ea3226c63fe5ef3e3dfc7da2279402da /kernel/sys.c | |
| parent | 4bbf9020becbfd8fc2c3da790855b7042fad455b (diff) | |
tracing: Add task_prctl_unknown tracepoint
prctl() is a complex syscall which multiplexes its functionality based
on a large set of PR_* options. Currently we count 64 such options. The
return value of unknown options is -EINVAL, and doesn't distinguish from
known options that were passed invalid args that also return -EINVAL.
To understand if programs are attempting to use prctl() options not yet
available on the running kernel, provide the task_prctl_unknown
tracepoint.
Note, this tracepoint is in an unlikely cold path, and would therefore
be suitable for continuous monitoring (e.g. via perf_event_open).
While the above is likely the simplest usecase, additionally this
tracepoint can help unlock some testing scenarios (where probing
sys_enter or sys_exit causes undesirable performance overheads):
a. unprivileged triggering of a test module: test modules may register a
probe to be called back on task_prctl_unknown, and pick a very large
unknown prctl() option upon which they perform a test function for an
unprivileged user;
b. unprivileged triggering of an eBPF program function: similar
as idea (a).
Example trace_pipe output:
test-380 [001] ..... 78.142904: task_prctl_unknown: option=1234 arg2=101 arg3=102 arg4=103 arg5=104
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Link: https://lore.kernel.org/r/20241108113455.2924361-1-elver@google.com
Signed-off-by: Kees Cook <kees@kernel.org>
Diffstat (limited to 'kernel/sys.c')
| -rw-r--r-- | kernel/sys.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/sys.c b/kernel/sys.c index c4c701c6f0b4..cb366ff8703a 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -75,6 +75,8 @@ #include <asm/io.h> #include <asm/unistd.h> +#include <trace/events/task.h> + #include "uid16.h" #ifndef SET_UNALIGN_CTL @@ -2810,6 +2812,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, error = arch_lock_shadow_stack_status(me, arg2); break; default: + trace_task_prctl_unknown(option, arg2, arg3, arg4, arg5); error = -EINVAL; break; } |