diff options
| author | Jiri Olsa <olsajiri@gmail.com> | 2025-05-14 12:18:09 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-08-15 16:39:16 +0200 |
| commit | 2fe136291081396fa96d53d77dea79ba55c1cdf6 (patch) | |
| tree | 4daf9da1363498f9b96634035fe8b8017f6f7775 | |
| parent | 953320b29d8ef31bb78f1d9ad57b8be9cbbdfb74 (diff) | |
uprobes: revert ref_ctr_offset in uprobe_unregister error path
[ Upstream commit aa644c405291a419e92b112e2279c01c410e9a26 ]
There's error path that could lead to inactive uprobe:
1) uprobe_register succeeds - updates instruction to int3 and
changes ref_ctr from 0 to 1
2) uprobe_unregister fails - int3 stays in place, but ref_ctr
is changed to 0 (it's not restored to 1 in the fail path)
uprobe is leaked
3) another uprobe_register comes and re-uses the leaked uprobe
and succeds - but int3 is already in place, so ref_ctr update
is skipped and it stays 0 - uprobe CAN NOT be triggered now
4) uprobe_unregister fails because ref_ctr value is unexpected
Fix this by reverting the updated ref_ctr value back to 1 in step 2),
which is the case when uprobe_unregister fails (int3 stays in place), but
we have already updated refctr.
The new scenario will go as follows:
1) uprobe_register succeeds - updates instruction to int3 and
changes ref_ctr from 0 to 1
2) uprobe_unregister fails - int3 stays in place and ref_ctr
is reverted to 1.. uprobe is leaked
3) another uprobe_register comes and re-uses the leaked uprobe
and succeds - but int3 is already in place, so ref_ctr update
is skipped and it stays 1 - uprobe CAN be triggered now
4) uprobe_unregister succeeds
Link: https://lkml.kernel.org/r/20250514101809.2010193-1-jolsa@kernel.org
Fixes: 1cc33161a83d ("uprobes: Support SDT markers having reference count (semaphore)")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | kernel/events/uprobes.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 4c965ba77f9f..84ee7b590861 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -581,8 +581,8 @@ retry: out: /* Revert back reference counter if instruction update failed. */ - if (ret < 0 && is_register && ref_ctr_updated) - update_ref_ctr(uprobe, mm, -1); + if (ret < 0 && ref_ctr_updated) + update_ref_ctr(uprobe, mm, is_register ? -1 : 1); /* try collapse pmd for compound page */ if (ret > 0) |