diff mbox series

[bpf,v5,1/2] bpf: fix unpopulated name_len field in perf_event link info

Message ID 20241006195131.563006-1-wudevelops@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series [bpf,v5,1/2] bpf: fix unpopulated name_len field in perf_event link info | expand

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Commit Message

Tyrone Wu Oct. 6, 2024, 7:51 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.

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>
Acked-by: Jiri Olsa <jolsa@kernel.org>
---
V4 -> V5:
Link: https://lore.kernel.org/bpf/CALOAHbC5xm7Cbfhau3z5X2PqUhiHECNWAPtJCWiOVqTKmdZp-Q@mail.gmail.com/
- Check that buf is not NULL before retrieving/using its length

V3 -> V4:
Link: https://lore.kernel.org/bpf/Zv_PP6Gs5cq3W2Ey@krava/
- Split patch into separate kernel and selftest change

V2 -> V3:
Link: https://lore.kernel.org/bpf/Zv7sISV0yEyGlEM3@krava/
- Use clearer variable name for user set/inputted name len (name_len -> input_len)
- Change (name_len -> input_len) type from size_t to u32 since it's only received and used as u32

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 | 38 ++++++++++++++++++++++++--------------
 1 file changed, 24 insertions(+), 14 deletions(-)

Comments

Yafang Shao Oct. 7, 2024, 2:09 a.m. UTC | #1 
On Mon, Oct 7, 2024 at 3:51 AM tyrone-wu <wudevelops@gmail.com> 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.
>
> 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>
> Acked-by: Jiri Olsa <jolsa@kernel.org>

LGTM
Acked-by: Yafang Shao <laoar.shao@gmail.com>

> ---
> V4 -> V5:
> Link: https://lore.kernel.org/bpf/CALOAHbC5xm7Cbfhau3z5X2PqUhiHECNWAPtJCWiOVqTKmdZp-Q@mail.gmail.com/
> - Check that buf is not NULL before retrieving/using its length
>
> V3 -> V4:
> Link: https://lore.kernel.org/bpf/Zv_PP6Gs5cq3W2Ey@krava/
> - Split patch into separate kernel and selftest change
>
> V2 -> V3:
> Link: https://lore.kernel.org/bpf/Zv7sISV0yEyGlEM3@krava/
> - Use clearer variable name for user set/inputted name len (name_len -> input_len)
> - Change (name_len -> input_len) type from size_t to u32 since it's only received and used as u32
>
> 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 | 38 ++++++++++++++++++++++++--------------
>  1 file changed, 24 insertions(+), 14 deletions(-)
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index a8f1808a1ca5..3df192a6bdcc 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -3565,32 +3565,35 @@ 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;
> +       u32 prog_id, input_len;
>         size_t 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;
> -       if (!uname)
> -               return 0;
> +
>         if (buf) {
> +               input_len = *ulen;
>                 len = strlen(buf);
> -               err = bpf_copy_to_user(uname, buf, ulen, len);
> -               if (err)
> -                       return err;
> -       } else {
> -               char zero = '\0';
> +               *ulen = len + 1;
>
> +               if (uname) {
> +                       err = bpf_copy_to_user(uname, buf, input_len, len);
> +                       if (err)
> +                               return err;
> +               }
> +       } else if (uname) {
> +               char zero = '\0';
>                 if (put_user(zero, uname))
>                         return -EFAULT;
>         }
> @@ -3609,7 +3612,7 @@ 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 +3620,7 @@ 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 +3642,7 @@ 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 +3651,7 @@ 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 +3677,18 @@ 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,
> --
> 2.43.0
>
Jiri Olsa Oct. 7, 2024, 8:07 a.m. UTC | #2 
On Sun, Oct 06, 2024 at 07:51:30PM +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.
> 
> 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>
> Acked-by: Jiri Olsa <jolsa@kernel.org>
> ---
> V4 -> V5:
> Link: https://lore.kernel.org/bpf/CALOAHbC5xm7Cbfhau3z5X2PqUhiHECNWAPtJCWiOVqTKmdZp-Q@mail.gmail.com/
> - Check that buf is not NULL before retrieving/using its length
> 
> V3 -> V4:
> Link: https://lore.kernel.org/bpf/Zv_PP6Gs5cq3W2Ey@krava/
> - Split patch into separate kernel and selftest change
> 
> V2 -> V3:
> Link: https://lore.kernel.org/bpf/Zv7sISV0yEyGlEM3@krava/
> - Use clearer variable name for user set/inputted name len (name_len -> input_len)
> - Change (name_len -> input_len) type from size_t to u32 since it's only received and used as u32
> 
> 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 | 38 ++++++++++++++++++++++++--------------
>  1 file changed, 24 insertions(+), 14 deletions(-)
> 
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index a8f1808a1ca5..3df192a6bdcc 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -3565,32 +3565,35 @@ 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;
> +	u32 prog_id, input_len;
>  	size_t 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;
> -	if (!uname)
> -		return 0;
> +
>  	if (buf) {
> +		input_len = *ulen;
>  		len = strlen(buf);
> -		err = bpf_copy_to_user(uname, buf, ulen, len);
> -		if (err)
> -			return err;
> -	} else {
> -		char zero = '\0';
> +		*ulen = len + 1;
>  
> +		if (uname) {
> +			err = bpf_copy_to_user(uname, buf, input_len, len);
> +			if (err)
> +				return err;
> +		}
> +	} else if (uname) {
> +		char zero = '\0';
>  		if (put_user(zero, uname))
>  			return -EFAULT;
>  	}

hm, why not just simple check buf for and keep the rest? seems less complicated..

jirka


---
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index a8f1808a1ca5..e393b94b90ec 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;
+	u32 prog_id, input_len;
 	size_t 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;
+	if (buf) {
+		input_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, input_len, len);
 		if (err)
 			return err;
 	} else {
diff mbox series

Patch

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index a8f1808a1ca5..3df192a6bdcc 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3565,32 +3565,35 @@  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;
+	u32 prog_id, input_len;
 	size_t 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;
-	if (!uname)
-		return 0;
+
 	if (buf) {
+		input_len = *ulen;
 		len = strlen(buf);
-		err = bpf_copy_to_user(uname, buf, ulen, len);
-		if (err)
-			return err;
-	} else {
-		char zero = '\0';
+		*ulen = len + 1;
 
+		if (uname) {
+			err = bpf_copy_to_user(uname, buf, input_len, len);
+			if (err)
+				return err;
+		}
+	} else if (uname) {
+		char zero = '\0';
 		if (put_user(zero, uname))
 			return -EFAULT;
 	}
@@ -3609,7 +3612,7 @@  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 +3620,7 @@  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 +3642,7 @@  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 +3651,7 @@  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 +3677,18 @@  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,