6.9-stable review patch. If anyone has any objections, please let me know.
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From: Andrii Nakryiko andrii@kernel.org
commit 46ba0e49b64232adac35a2bc892f1710c5b0fb7f upstream.
Current implementation of PID filtering logic for multi-uprobes in uprobe_prog_run() is filtering down to exact *thread*, while the intent for PID filtering it to filter by *process* instead. The check in uprobe_prog_run() also differs from the analogous one in uprobe_multi_link_filter() for some reason. The latter is correct, checking task->mm, not the task itself.
Fix the check in uprobe_prog_run() to perform the same task->mm check.
While doing this, we also update get_pid_task() use to use PIDTYPE_TGID type of lookup, given the intent is to get a representative task of an entire process. This doesn't change behavior, but seems more logical. It would hold task group leader task now, not any random thread task.
Last but not least, given multi-uprobe support is half-broken due to this PID filtering logic (depending on whether PID filtering is important or not), we need to make it easy for user space consumers (including libbpf) to easily detect whether PID filtering logic was already fixed.
We do it here by adding an early check on passed pid parameter. If it's negative (and so has no chance of being a valid PID), we return -EINVAL. Previous behavior would eventually return -ESRCH ("No process found"), given there can't be any process with negative PID. This subtle change won't make any practical change in behavior, but will allow applications to detect PID filtering fixes easily. Libbpf fixes take advantage of this in the next patch.
Cc: stable@vger.kernel.org Acked-by: Jiri Olsa jolsa@kernel.org Fixes: b733eeade420 ("bpf: Add pid filter support for uprobe_multi link") Signed-off-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/r/20240521163401.3005045-2-andrii@kernel.org Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/trace/bpf_trace.c | 8 ++++---- tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c | 2 +- 2 files changed, 5 insertions(+), 5 deletions(-)
--- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -3260,7 +3260,7 @@ static int uprobe_prog_run(struct bpf_up struct bpf_run_ctx *old_run_ctx; int err = 0;
- if (link->task && current != link->task) + if (link->task && current->mm != link->task->mm) return 0;
if (sleepable) @@ -3361,8 +3361,9 @@ int bpf_uprobe_multi_link_attach(const u upath = u64_to_user_ptr(attr->link_create.uprobe_multi.path); uoffsets = u64_to_user_ptr(attr->link_create.uprobe_multi.offsets); cnt = attr->link_create.uprobe_multi.cnt; + pid = attr->link_create.uprobe_multi.pid;
- if (!upath || !uoffsets || !cnt) + if (!upath || !uoffsets || !cnt || pid < 0) return -EINVAL; if (cnt > MAX_UPROBE_MULTI_CNT) return -E2BIG; @@ -3386,10 +3387,9 @@ int bpf_uprobe_multi_link_attach(const u goto error_path_put; }
- pid = attr->link_create.uprobe_multi.pid; if (pid) { rcu_read_lock(); - task = get_pid_task(find_vpid(pid), PIDTYPE_PID); + task = get_pid_task(find_vpid(pid), PIDTYPE_TGID); rcu_read_unlock(); if (!task) { err = -ESRCH; --- a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c @@ -397,7 +397,7 @@ static void test_attach_api_fails(void) link_fd = bpf_link_create(prog_fd, 0, BPF_TRACE_UPROBE_MULTI, &opts); if (!ASSERT_ERR(link_fd, "link_fd")) goto cleanup; - ASSERT_EQ(link_fd, -ESRCH, "pid_is_wrong"); + ASSERT_EQ(link_fd, -EINVAL, "pid_is_wrong");
cleanup: if (link_fd >= 0)