On Mon, Dec 16, 2024 at 10:39:46AM +0100, Jiri Olsa wrote:
On Sun, Dec 15, 2024 at 10:02:07AM +0100, gregkh@linuxfoundation.org wrote:
The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
hi, there's conflict because 5.15.y is not getting [1] fix (because 5.15.y does not have [2]), I'll send new backport
after digging deeper I don't think we need this fix on 5.15, because we don't have [1] in 5.15, which allows to inherit tracing programs, in this hunk:
#if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_EVENT_TRACING) - if (overflow_handler == bpf_overflow_handler) { + if (parent_event->prog) { struct bpf_prog *prog = parent_event->prog;
bpf_prog_inc(prog); event->prog = prog;
before this fix (5.15) we allow it only for perf_event programs, which is safe, I'll check and send separate upstream fix to handle attr.inherit for tracing programs
thanks, jirka
[1] f11f10bfa1ca perf/bpf: Call BPF handler directly, not through overflow machinery
jirka
[1] ef1b808e3b7c bpf: Fix UAF via mismatching bpf_prog/attachment RCU flavors [2] 8c7dcb84e3b7 bpf: implement sleepable uprobes by chaining gps
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 978c4486cca5c7b9253d3ab98a88c8e769cb9bbd # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024121506-pancreas-mosaic-0ae0@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 978c4486cca5c7b9253d3ab98a88c8e769cb9bbd Mon Sep 17 00:00:00 2001 From: Jiri Olsa jolsa@kernel.org Date: Sun, 8 Dec 2024 15:25:07 +0100 Subject: [PATCH] bpf,perf: Fix invalid prog_array access in perf_event_detach_bpf_prog
Syzbot reported [1] crash that happens for following tracing scenario:
create tracepoint perf event with attr.inherit=1, attach it to the process and set bpf program to it
attached process forks -> chid creates inherited event
the new child event shares the parent's bpf program and tp_event (hence prog_array) which is global for tracepoint
exit both process and its child -> release both events
first perf_event_detach_bpf_prog call will release tp_event->prog_array and second perf_event_detach_bpf_prog will crash, because tp_event->prog_array is NULL
The fix makes sure the perf_event_detach_bpf_prog checks prog_array is valid before it tries to remove the bpf program from it.
[1] https://lore.kernel.org/bpf/Z1MR6dCIKajNS6nU@krava/T/#m91dbf0688221ec7a7fc95...
Fixes: 0ee288e69d03 ("bpf,perf: Fix perf_event_detach_bpf_prog error handling") Reported-by: syzbot+2e0d2840414ce817aaac@syzkaller.appspotmail.com Signed-off-by: Jiri Olsa jolsa@kernel.org Signed-off-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/bpf/20241208142507.1207698-1-jolsa@kernel.org
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index a403b05a7091..1b8db5aee9d3 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2250,6 +2250,9 @@ void perf_event_detach_bpf_prog(struct perf_event *event) goto unlock; old_array = bpf_event_rcu_dereference(event->tp_event->prog_array);
- if (!old_array)
goto put;- ret = bpf_prog_array_copy(old_array, event->prog, NULL, 0, &new_array); if (ret < 0) { bpf_prog_array_delete_safe(old_array, event->prog);
@@ -2258,6 +2261,7 @@ void perf_event_detach_bpf_prog(struct perf_event *event) bpf_prog_array_free_sleepable(old_array); } +put: /* * It could be that the bpf_prog is not sleepable (and will be freed * via normal RCU), but is called from a point that supports sleepable