diff mbox series

[bpf,v2] bpf: fix unpopulated name_len field in perf_event link info

Message ID 20241002213839.13790-1-wudevelops@gmail.com (mailing list archive)
State New
Headers show
Series [bpf,v2] bpf: fix unpopulated name_len field in perf_event link info | expand

Commit Message

Tyrone Wu Oct. 2, 2024, 9:38 p.m. UTC 
Previously when retrieving `bpf_link_info.perf_event` for
kprobe/uprobe/tracepoint, the `name_len` field was not populated by the
kernel, leaving it to reflect the value initially set by the user. This
behavior was inconsistent with how other input/output string buffer
fields function (e.g. `raw_tracepoint.tp_name_len`).

This patch fills `name_len` with the actual size of the string name. The
 relevant selftests have also been updated to assert that `name_len`
contains the correct size rather than 0.

Link: https://lore.kernel.org/bpf/CABVU1kXwQXhqQGe0RTrr7eegtM6SVW_KayZBy16-yb0Snztmtg@mail.gmail.com/
Fixes: 1b715e1b0ec5 ("bpf: Support ->fill_link_info for perf_event")
Signed-off-by: tyrone-wu <wudevelops@gmail.com>
---
V1 -> V2:
Link: https://lore.kernel.org/bpf/Zv0wl-S13WJnIkb_@krava/
- Use user set *ulen in bpf_copy_to_user before overwriting *ulen

 kernel/bpf/syscall.c                          | 29 +++++++++++++------
 .../selftests/bpf/prog_tests/fill_link_info.c |  6 ++--
 2 files changed, 23 insertions(+), 12 deletions(-)

Comments

Jiri Olsa Oct. 3, 2024, 7:10 p.m. UTC | #1 
On Wed, Oct 02, 2024 at 09:38:39PM +0000, tyrone-wu wrote:
> Previously when retrieving `bpf_link_info.perf_event` for
> kprobe/uprobe/tracepoint, the `name_len` field was not populated by the
> kernel, leaving it to reflect the value initially set by the user. This
> behavior was inconsistent with how other input/output string buffer
> fields function (e.g. `raw_tracepoint.tp_name_len`).
> 
> This patch fills `name_len` with the actual size of the string name. The
>  relevant selftests have also been updated to assert that `name_len`
> contains the correct size rather than 0.
> 
> Link: https://lore.kernel.org/bpf/CABVU1kXwQXhqQGe0RTrr7eegtM6SVW_KayZBy16-yb0Snztmtg@mail.gmail.com/
> Fixes: 1b715e1b0ec5 ("bpf: Support ->fill_link_info for perf_event")
> Signed-off-by: tyrone-wu <wudevelops@gmail.com>
> ---
> V1 -> V2:
> Link: https://lore.kernel.org/bpf/Zv0wl-S13WJnIkb_@krava/
> - Use user set *ulen in bpf_copy_to_user before overwriting *ulen
> 
>  kernel/bpf/syscall.c                          | 29 +++++++++++++------
>  .../selftests/bpf/prog_tests/fill_link_info.c |  6 ++--
>  2 files changed, 23 insertions(+), 12 deletions(-)
> 
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index a8f1808a1ca5..26cc18693924 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -3565,27 +3565,31 @@ static void bpf_perf_link_dealloc(struct bpf_link *link)
>  }
>  
>  static int bpf_perf_link_fill_common(const struct perf_event *event,
> -				     char __user *uname, u32 ulen,
> +				     char __user *uname, u32 *ulen,
>  				     u64 *probe_offset, u64 *probe_addr,
>  				     u32 *fd_type, unsigned long *missed)
>  {
>  	const char *buf;
>  	u32 prog_id;
> -	size_t len;
> +	size_t len, name_len;

>  	int err;
>  
> -	if (!ulen ^ !uname)
> +	if (!(*ulen) ^ !uname)
>  		return -EINVAL;
>  
>  	err = bpf_get_perf_event_info(event, &prog_id, fd_type, &buf,
>  				      probe_offset, probe_addr, missed);
>  	if (err)
>  		return err;
> +
> +	name_len = *ulen;
> +	len = strlen(buf);
> +	*ulen = len + 1;
>  	if (!uname)
>  		return 0;
> +
>  	if (buf) {
> -		len = strlen(buf);
> -		err = bpf_copy_to_user(uname, buf, ulen, len);
> +		err = bpf_copy_to_user(uname, buf, name_len, len);
>  		if (err)
>  			return err;
>  	} else {

small nit.. up to you but I'd suggest bit different naming like below,
otherwise looks good

Acked-by: Jiri Olsa <jolsa@kernel.org>

thanks,
jirka


---
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index a8f1808a1ca5..b637e9dced5a 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3565,26 +3565,28 @@ static void bpf_perf_link_dealloc(struct bpf_link *link)
 }
 
 static int bpf_perf_link_fill_common(const struct perf_event *event,
-				     char __user *uname, u32 ulen,
+				     char __user *uname, u32 *ulenp,
 				     u64 *probe_offset, u64 *probe_addr,
 				     u32 *fd_type, unsigned long *missed)
 {
 	const char *buf;
-	u32 prog_id;
+	u32 prog_id, ulen;
 	size_t len;
 	int err;
 
-	if (!ulen ^ !uname)
+	if (!(*ulenp) ^ !uname)
 		return -EINVAL;
 
 	err = bpf_get_perf_event_info(event, &prog_id, fd_type, &buf,
 				      probe_offset, probe_addr, missed);
 	if (err)
 		return err;
+	ulen = *ulenp;
+	len = strlen(buf);
+	*ulenp = len + 1;
 	if (!uname)
 		return 0;
 	if (buf) {
-		len = strlen(buf);
 		err = bpf_copy_to_user(uname, buf, ulen, len);
 		if (err)
 			return err;
diff mbox series

Patch

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index a8f1808a1ca5..26cc18693924 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3565,27 +3565,31 @@  static void bpf_perf_link_dealloc(struct bpf_link *link)
 }
 
 static int bpf_perf_link_fill_common(const struct perf_event *event,
-				     char __user *uname, u32 ulen,
+				     char __user *uname, u32 *ulen,
 				     u64 *probe_offset, u64 *probe_addr,
 				     u32 *fd_type, unsigned long *missed)
 {
 	const char *buf;
 	u32 prog_id;
-	size_t len;
+	size_t len, name_len;
 	int err;
 
-	if (!ulen ^ !uname)
+	if (!(*ulen) ^ !uname)
 		return -EINVAL;
 
 	err = bpf_get_perf_event_info(event, &prog_id, fd_type, &buf,
 				      probe_offset, probe_addr, missed);
 	if (err)
 		return err;
+
+	name_len = *ulen;
+	len = strlen(buf);
+	*ulen = len + 1;
 	if (!uname)
 		return 0;
+
 	if (buf) {
-		len = strlen(buf);
-		err = bpf_copy_to_user(uname, buf, ulen, len);
+		err = bpf_copy_to_user(uname, buf, name_len, len);
 		if (err)
 			return err;
 	} else {
@@ -3609,7 +3613,7 @@  static int bpf_perf_link_fill_kprobe(const struct perf_event *event,
 
 	uname = u64_to_user_ptr(info->perf_event.kprobe.func_name);
 	ulen = info->perf_event.kprobe.name_len;
-	err = bpf_perf_link_fill_common(event, uname, ulen, &offset, &addr,
+	err = bpf_perf_link_fill_common(event, uname, &ulen, &offset, &addr,
 					&type, &missed);
 	if (err)
 		return err;
@@ -3617,7 +3621,7 @@  static int bpf_perf_link_fill_kprobe(const struct perf_event *event,
 		info->perf_event.type = BPF_PERF_EVENT_KRETPROBE;
 	else
 		info->perf_event.type = BPF_PERF_EVENT_KPROBE;
-
+	info->perf_event.kprobe.name_len = ulen;
 	info->perf_event.kprobe.offset = offset;
 	info->perf_event.kprobe.missed = missed;
 	if (!kallsyms_show_value(current_cred()))
@@ -3639,7 +3643,7 @@  static int bpf_perf_link_fill_uprobe(const struct perf_event *event,
 
 	uname = u64_to_user_ptr(info->perf_event.uprobe.file_name);
 	ulen = info->perf_event.uprobe.name_len;
-	err = bpf_perf_link_fill_common(event, uname, ulen, &offset, &addr,
+	err = bpf_perf_link_fill_common(event, uname, &ulen, &offset, &addr,
 					&type, NULL);
 	if (err)
 		return err;
@@ -3648,6 +3652,7 @@  static int bpf_perf_link_fill_uprobe(const struct perf_event *event,
 		info->perf_event.type = BPF_PERF_EVENT_URETPROBE;
 	else
 		info->perf_event.type = BPF_PERF_EVENT_UPROBE;
+	info->perf_event.uprobe.name_len = ulen;
 	info->perf_event.uprobe.offset = offset;
 	info->perf_event.uprobe.cookie = event->bpf_cookie;
 	return 0;
@@ -3673,12 +3678,18 @@  static int bpf_perf_link_fill_tracepoint(const struct perf_event *event,
 {
 	char __user *uname;
 	u32 ulen;
+	int err;
 
 	uname = u64_to_user_ptr(info->perf_event.tracepoint.tp_name);
 	ulen = info->perf_event.tracepoint.name_len;
+	err = bpf_perf_link_fill_common(event, uname, &ulen, NULL, NULL, NULL, NULL);
+	if (err)
+		return err;
+
 	info->perf_event.type = BPF_PERF_EVENT_TRACEPOINT;
+	info->perf_event.tracepoint.name_len = ulen;
 	info->perf_event.tracepoint.cookie = event->bpf_cookie;
-	return bpf_perf_link_fill_common(event, uname, ulen, NULL, NULL, NULL, NULL);
+	return 0;
 }
 
 static int bpf_perf_link_fill_perf_event(const struct perf_event *event,
diff --git a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
index f3932941bbaa..59077f260404 100644
--- a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
+++ b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
@@ -67,8 +67,8 @@  static int verify_perf_link_info(int fd, enum bpf_perf_event_type type, long add
 
 		ASSERT_EQ(info.perf_event.kprobe.cookie, PERF_EVENT_COOKIE, "kprobe_cookie");
 
+		ASSERT_EQ(info.perf_event.kprobe.name_len, strlen(KPROBE_FUNC) + 1, "name_len");
 		if (!info.perf_event.kprobe.func_name) {
-			ASSERT_EQ(info.perf_event.kprobe.name_len, 0, "name_len");
 			info.perf_event.kprobe.func_name = ptr_to_u64(&buf);
 			info.perf_event.kprobe.name_len = sizeof(buf);
 			goto again;
@@ -79,8 +79,8 @@  static int verify_perf_link_info(int fd, enum bpf_perf_event_type type, long add
 		ASSERT_EQ(err, 0, "cmp_kprobe_func_name");
 		break;
 	case BPF_PERF_EVENT_TRACEPOINT:
+		ASSERT_EQ(info.perf_event.tracepoint.name_len, strlen(TP_NAME) + 1, "name_len");
 		if (!info.perf_event.tracepoint.tp_name) {
-			ASSERT_EQ(info.perf_event.tracepoint.name_len, 0, "name_len");
 			info.perf_event.tracepoint.tp_name = ptr_to_u64(&buf);
 			info.perf_event.tracepoint.name_len = sizeof(buf);
 			goto again;
@@ -96,8 +96,8 @@  static int verify_perf_link_info(int fd, enum bpf_perf_event_type type, long add
 	case BPF_PERF_EVENT_URETPROBE:
 		ASSERT_EQ(info.perf_event.uprobe.offset, offset, "uprobe_offset");
 
+		ASSERT_EQ(info.perf_event.uprobe.name_len, strlen(UPROBE_FILE) + 1, "name_len");
 		if (!info.perf_event.uprobe.file_name) {
-			ASSERT_EQ(info.perf_event.uprobe.name_len, 0, "name_len");
 			info.perf_event.uprobe.file_name = ptr_to_u64(&buf);
 			info.perf_event.uprobe.name_len = sizeof(buf);
 			goto again;