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bpf: Fix unpopulated path_size when uprobe_multi fields unset

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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: e56fdbfb06 ("bpf: Add link_info support for uprobe multi link")
Signed-off-by: Tyrone Wu <wudevelops@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241011000803.681190-1-wudevelops@gmail.com
This commit is contained in:
Tyrone Wu 2024-10-11 00:08:02 +00:00 committed by Andrii Nakryiko
parent fd526e121c
commit ad6b5b6ea9
1 changed files with 17 additions and 19 deletions
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36
kernel/trace/bpf_trace.c
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@ -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;
@ -3147,26 +3148,23 @@ 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);
buf = kmalloc(upath_size, GFP_KERNEL);
if (!buf)
return -ENOMEM;
p = d_path(&umulti_link->path, buf, upath_size);
if (IS_ERR(p)) {
kfree(buf);
return PTR_ERR(p);
}
upath_size = buf + upath_size - p;
left = copy_to_user(upath, p, upath_size);
upath_size = upath_size ? min_t(u32, upath_size, PATH_MAX) : PATH_MAX;
buf = kmalloc(upath_size, GFP_KERNEL);
if (!buf)
return -ENOMEM;
p = d_path(&umulti_link->path, buf, upath_size);
if (IS_ERR(p)) {
kfree(buf);
if (left)
return -EFAULT;
info->uprobe_multi.path_size = upath_size;
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;