Commit ad6b5b6e authored by Tyrone Wu's avatar Tyrone Wu Committed by Andrii Nakryiko
Browse files

bpf: Fix unpopulated path_size when uprobe_multi fields unset 



Previously when retrieving `bpf_link_info.uprobe_multi` with `path` and
`path_size` fields unset, the `path_size` field is not populated
(remains 0). This behavior was inconsistent with how other input/output
string buffer fields work, as the field should be populated in cases
when:
- both buffer and length are set (currently works as expected)
- both buffer and length are unset (not working as expected)

This patch now fills the `path_size` field when `path` and `path_size`
are unset.

Fixes: e56fdbfb ("bpf: Add link_info support for uprobe multi link")
Signed-off-by: default avatarTyrone Wu <wudevelops@gmail.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241011000803.681190-1-wudevelops@gmail.com
parent fd526e12

kernel/trace/bpf_trace.c

+17 −19
Original line number Diff line number Diff line
@@ -3133,7 +3133,8 @@ static int bpf_uprobe_multi_link_fill_link_info(const struct bpf_link *link, 
	struct bpf_uprobe_multi_link *umulti_link;

	u32 ucount = info->uprobe_multi.count;

	int err = 0, i;

	long left;

	char *p, *buf;

	long left = 0;



	if (!upath ^ !upath_size)

		return -EINVAL;
@@ -3147,11 +3148,7 @@ static int bpf_uprobe_multi_link_fill_link_info(const struct bpf_link *link, 
	info->uprobe_multi.pid = umulti_link->task ?

				 task_pid_nr_ns(umulti_link->task, task_active_pid_ns(current)) : 0;



	if (upath) {

		char *p, *buf;



		upath_size = min_t(u32, upath_size, PATH_MAX);



	upath_size = upath_size ? min_t(u32, upath_size, PATH_MAX) : PATH_MAX;

	buf = kmalloc(upath_size, GFP_KERNEL);

	if (!buf)

		return -ENOMEM;
@@ -3161,12 +3158,13 @@ static int bpf_uprobe_multi_link_fill_link_info(const struct bpf_link *link, 
		return PTR_ERR(p);

	}

	upath_size = buf + upath_size - p;



	if (upath)

		left = copy_to_user(upath, p, upath_size);

	kfree(buf);

	if (left)

		return -EFAULT;

	info->uprobe_multi.path_size = upath_size;

	}



	if (!uoffsets && !ucookies && !uref_ctr_offsets)

		return 0;