diff mbox series

[bpf-next] bpf: check bpf_map/bpf_program fd validity

Message ID 20240318131808.95959-1-yatsenko@meta.com (mailing list archive)
State Accepted
Commit 7b30c296af6525571fc967f6a8661f6e1127369e
Delegated to: BPF
Headers show
Series [bpf-next] bpf: check bpf_map/bpf_program fd validity | expand

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netdev/fixes_present success Fixes tag not required for -next series
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netdev/verify_fixes success No Fixes tag
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netdev/checkpatch warning WARNING: line length of 94 exceeds 80 columns WARNING: line length of 97 exceeds 80 columns
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Commit Message

Mykyta Yatsenko mykyta.yatsenko5@gmail.com March 18, 2024, 1:18 p.m. UTC 
From: Mykyta Yatsenko <yatsenko@meta.com>

libbpf creates bpf_program/bpf_map structs for each program/map that
user defines, but it allows to disable creating/loading those objects in
kernel, in that case they won't have associated file descriptor
(fd < 0). Such functionality is used for backward compatibility
with some older kernels.

Nothing prevents users from passing these maps or programs with no
kernel counterpart to libbpf APIs. This change introduces explicit
checks for kernel objects existence, aiming to improve visibility of
those edge cases and provide meaningful warnings to users.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
---
 tools/lib/bpf/libbpf.c | 56 ++++++++++++++++++++++++++++++++++++++----
 1 file changed, 51 insertions(+), 5 deletions(-)

Comments

Andrii Nakryiko March 18, 2024, 8:50 p.m. UTC | #1 
On Mon, Mar 18, 2024 at 6:18 AM Mykyta Yatsenko
<mykyta.yatsenko5@gmail.com> wrote:
>

We generally use "libbpf: " prefix for patch subject if changes are
related to libbpf code base. I fixed it up while applying.

> From: Mykyta Yatsenko <yatsenko@meta.com>
>
> libbpf creates bpf_program/bpf_map structs for each program/map that
> user defines, but it allows to disable creating/loading those objects in
> kernel, in that case they won't have associated file descriptor
> (fd < 0). Such functionality is used for backward compatibility
> with some older kernels.
>
> Nothing prevents users from passing these maps or programs with no
> kernel counterpart to libbpf APIs. This change introduces explicit
> checks for kernel objects existence, aiming to improve visibility of
> those edge cases and provide meaningful warnings to users.
>
> Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
> ---
>  tools/lib/bpf/libbpf.c | 56 ++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 51 insertions(+), 5 deletions(-)
>

See nits below. I fixed all that up while applying, as it was just
some text adjustment, so it didn't seem worth another version. Thanks
for the patch, it will help users!

> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 604368cfbf02..d1febdb036de 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -8572,6 +8572,12 @@ int bpf_map__pin(struct bpf_map *map, const char *path)
>                 return libbpf_err(-EINVAL);
>         }
>
> +       if (map->fd < 0) {
> +               pr_warn("map '%s': can't pin BPF map without FD (was it created?)\n",
> +                       bpf_map__name(map));
> +               return libbpf_err(-EINVAL);
> +       }
> +
>         if (map->pin_path) {
>                 if (path && strcmp(path, map->pin_path)) {
>                         pr_warn("map '%s' already has pin path '%s' different from '%s'\n",
> @@ -10316,6 +10322,11 @@ static int validate_map_op(const struct bpf_map *map, size_t key_sz,
>                 return -EINVAL;
>         }
>
> +       if (map->fd < 0) {
> +               pr_warn("map '%s': can't use BPF map without FD (was it created?)\n", map->name);
> +               return -EINVAL;
> +       }
> +
>         if (!check_value_sz)
>                 return 0;
>
> @@ -10428,8 +10439,15 @@ long libbpf_get_error(const void *ptr)
>  int bpf_link__update_program(struct bpf_link *link, struct bpf_program *prog)
>  {
>         int ret;
> +       int prog_fd = bpf_program__fd(prog);
>
> -       ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog), NULL);
> +       if (prog_fd < 0) {
> +               pr_warn("prog '%s': can't use BPF program without FD (was it created?)\n",

maps are created, programs are loaded, so "was it loaded?"?

> +                       prog->name);
> +               return libbpf_err(-EINVAL);
> +       }
> +
> +       ret = bpf_link_update(bpf_link__fd(link), prog_fd, NULL);
>         return libbpf_err_errno(ret);
>  }
>
> @@ -11347,6 +11365,13 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
>         if (!OPTS_VALID(opts, bpf_kprobe_multi_opts))
>                 return libbpf_err_ptr(-EINVAL);
>
> +       prog_fd = bpf_program__fd(prog);
> +       if (prog_fd < 0) {
> +               pr_warn("prog '%s': can't attach BPF program without FD (was it created?)\n",

ditto

> +                       prog->name);
> +               return libbpf_err_ptr(-EINVAL);
> +       }
> +
>         syms    = OPTS_GET(opts, syms, false);
>         addrs   = OPTS_GET(opts, addrs, false);
>         cnt     = OPTS_GET(opts, cnt, false);
> @@ -11387,7 +11412,6 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
>         }
>         link->detach = &bpf_link__detach_fd;
>
> -       prog_fd = bpf_program__fd(prog);
>         link_fd = bpf_link_create(prog_fd, 0, BPF_TRACE_KPROBE_MULTI, &lopts);
>         if (link_fd < 0) {
>                 err = -errno;
> @@ -11770,6 +11794,13 @@ bpf_program__attach_uprobe_multi(const struct bpf_program *prog,
>         if (!OPTS_VALID(opts, bpf_uprobe_multi_opts))
>                 return libbpf_err_ptr(-EINVAL);
>
> +       prog_fd = bpf_program__fd(prog);
> +       if (prog_fd < 0) {
> +               pr_warn("prog '%s': can't attach BPF program without FD (was it created?)\n",

loaded

> +                       prog->name);
> +               return libbpf_err_ptr(-EINVAL);
> +       }
> +
>         syms = OPTS_GET(opts, syms, NULL);
>         offsets = OPTS_GET(opts, offsets, NULL);
>         ref_ctr_offsets = OPTS_GET(opts, ref_ctr_offsets, NULL);
> @@ -11845,7 +11876,6 @@ bpf_program__attach_uprobe_multi(const struct bpf_program *prog,
>         }
>         link->detach = &bpf_link__detach_fd;
>
> -       prog_fd = bpf_program__fd(prog);
>         link_fd = bpf_link_create(prog_fd, 0, BPF_TRACE_UPROBE_MULTI, &lopts);
>         if (link_fd < 0) {
>                 err = -errno;
> @@ -12671,6 +12701,12 @@ struct bpf_link *bpf_program__attach(const struct bpf_program *prog)
>         if (!prog->sec_def || !prog->sec_def->prog_attach_fn)
>                 return libbpf_err_ptr(-EOPNOTSUPP);
>
> +       if (bpf_program__fd(prog) < 0) {
> +               pr_warn("prog '%s': can't attach BPF program w/o FD (did you load it?)\n",

I normalized w/o to without

> +                       prog->name);
> +               return libbpf_err_ptr(-EINVAL);
> +       }
> +
>         err = prog->sec_def->prog_attach_fn(prog, prog->sec_def->cookie, &link);
>         if (err)
>                 return libbpf_err_ptr(err);
> @@ -12711,9 +12747,14 @@ struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
>         __u32 zero = 0;
>         int err, fd;
>
> -       if (!bpf_map__is_struct_ops(map) || map->fd == -1)
> +       if (!bpf_map__is_struct_ops(map))
>                 return libbpf_err_ptr(-EINVAL);
>
> +       if (map->fd < 0) {
> +               pr_warn("map '%s': can't attach BPF map w/o FD (did you load it?)\n", map->name);

without, "was it created?"

> +               return libbpf_err_ptr(-EINVAL);
> +       }
> +
>         link = calloc(1, sizeof(*link));
>         if (!link)
>                 return libbpf_err_ptr(-EINVAL);
> @@ -12760,8 +12801,13 @@ int bpf_link__update_map(struct bpf_link *link, const struct bpf_map *map)
>         __u32 zero = 0;
>         int err;
>
> -       if (!bpf_map__is_struct_ops(map) || !map_is_created(map))
> +       if (!bpf_map__is_struct_ops(map))
> +               return -EINVAL;
> +
> +       if (map->fd < 0) {
> +               pr_warn("map '%s': can't use BPF map w/o FD (did you load it?)\n", map->name);

same about create vs load

>                 return -EINVAL;
> +       }
>
>         st_ops_link = container_of(link, struct bpf_link_struct_ops, link);
>         /* Ensure the type of a link is correct */
> --
> 2.42.0
>
patchwork-bot+netdevbpf@kernel.org March 18, 2024, 9 p.m. UTC | #2 
Hello:

This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Mon, 18 Mar 2024 13:18:08 +0000 you wrote:
> From: Mykyta Yatsenko <yatsenko@meta.com>
> 
> libbpf creates bpf_program/bpf_map structs for each program/map that
> user defines, but it allows to disable creating/loading those objects in
> kernel, in that case they won't have associated file descriptor
> (fd < 0). Such functionality is used for backward compatibility
> with some older kernels.
> 
> [...]

Here is the summary with links:
  - [bpf-next] bpf: check bpf_map/bpf_program fd validity
    https://git.kernel.org/bpf/bpf-next/c/7b30c296af65

You are awesome, thank you!
diff mbox series

Patch

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 604368cfbf02..d1febdb036de 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -8572,6 +8572,12 @@  int bpf_map__pin(struct bpf_map *map, const char *path)
 		return libbpf_err(-EINVAL);
 	}
 
+	if (map->fd < 0) {
+		pr_warn("map '%s': can't pin BPF map without FD (was it created?)\n",
+			bpf_map__name(map));
+		return libbpf_err(-EINVAL);
+	}
+
 	if (map->pin_path) {
 		if (path && strcmp(path, map->pin_path)) {
 			pr_warn("map '%s' already has pin path '%s' different from '%s'\n",
@@ -10316,6 +10322,11 @@  static int validate_map_op(const struct bpf_map *map, size_t key_sz,
 		return -EINVAL;
 	}
 
+	if (map->fd < 0) {
+		pr_warn("map '%s': can't use BPF map without FD (was it created?)\n", map->name);
+		return -EINVAL;
+	}
+
 	if (!check_value_sz)
 		return 0;
 
@@ -10428,8 +10439,15 @@  long libbpf_get_error(const void *ptr)
 int bpf_link__update_program(struct bpf_link *link, struct bpf_program *prog)
 {
 	int ret;
+	int prog_fd = bpf_program__fd(prog);
 
-	ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog), NULL);
+	if (prog_fd < 0) {
+		pr_warn("prog '%s': can't use BPF program without FD (was it created?)\n",
+			prog->name);
+		return libbpf_err(-EINVAL);
+	}
+
+	ret = bpf_link_update(bpf_link__fd(link), prog_fd, NULL);
 	return libbpf_err_errno(ret);
 }
 
@@ -11347,6 +11365,13 @@  bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
 	if (!OPTS_VALID(opts, bpf_kprobe_multi_opts))
 		return libbpf_err_ptr(-EINVAL);
 
+	prog_fd = bpf_program__fd(prog);
+	if (prog_fd < 0) {
+		pr_warn("prog '%s': can't attach BPF program without FD (was it created?)\n",
+			prog->name);
+		return libbpf_err_ptr(-EINVAL);
+	}
+
 	syms    = OPTS_GET(opts, syms, false);
 	addrs   = OPTS_GET(opts, addrs, false);
 	cnt     = OPTS_GET(opts, cnt, false);
@@ -11387,7 +11412,6 @@  bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
 	}
 	link->detach = &bpf_link__detach_fd;
 
-	prog_fd = bpf_program__fd(prog);
 	link_fd = bpf_link_create(prog_fd, 0, BPF_TRACE_KPROBE_MULTI, &lopts);
 	if (link_fd < 0) {
 		err = -errno;
@@ -11770,6 +11794,13 @@  bpf_program__attach_uprobe_multi(const struct bpf_program *prog,
 	if (!OPTS_VALID(opts, bpf_uprobe_multi_opts))
 		return libbpf_err_ptr(-EINVAL);
 
+	prog_fd = bpf_program__fd(prog);
+	if (prog_fd < 0) {
+		pr_warn("prog '%s': can't attach BPF program without FD (was it created?)\n",
+			prog->name);
+		return libbpf_err_ptr(-EINVAL);
+	}
+
 	syms = OPTS_GET(opts, syms, NULL);
 	offsets = OPTS_GET(opts, offsets, NULL);
 	ref_ctr_offsets = OPTS_GET(opts, ref_ctr_offsets, NULL);
@@ -11845,7 +11876,6 @@  bpf_program__attach_uprobe_multi(const struct bpf_program *prog,
 	}
 	link->detach = &bpf_link__detach_fd;
 
-	prog_fd = bpf_program__fd(prog);
 	link_fd = bpf_link_create(prog_fd, 0, BPF_TRACE_UPROBE_MULTI, &lopts);
 	if (link_fd < 0) {
 		err = -errno;
@@ -12671,6 +12701,12 @@  struct bpf_link *bpf_program__attach(const struct bpf_program *prog)
 	if (!prog->sec_def || !prog->sec_def->prog_attach_fn)
 		return libbpf_err_ptr(-EOPNOTSUPP);
 
+	if (bpf_program__fd(prog) < 0) {
+		pr_warn("prog '%s': can't attach BPF program w/o FD (did you load it?)\n",
+			prog->name);
+		return libbpf_err_ptr(-EINVAL);
+	}
+
 	err = prog->sec_def->prog_attach_fn(prog, prog->sec_def->cookie, &link);
 	if (err)
 		return libbpf_err_ptr(err);
@@ -12711,9 +12747,14 @@  struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
 	__u32 zero = 0;
 	int err, fd;
 
-	if (!bpf_map__is_struct_ops(map) || map->fd == -1)
+	if (!bpf_map__is_struct_ops(map))
 		return libbpf_err_ptr(-EINVAL);
 
+	if (map->fd < 0) {
+		pr_warn("map '%s': can't attach BPF map w/o FD (did you load it?)\n", map->name);
+		return libbpf_err_ptr(-EINVAL);
+	}
+
 	link = calloc(1, sizeof(*link));
 	if (!link)
 		return libbpf_err_ptr(-EINVAL);
@@ -12760,8 +12801,13 @@  int bpf_link__update_map(struct bpf_link *link, const struct bpf_map *map)
 	__u32 zero = 0;
 	int err;
 
-	if (!bpf_map__is_struct_ops(map) || !map_is_created(map))
+	if (!bpf_map__is_struct_ops(map))
+		return -EINVAL;
+
+	if (map->fd < 0) {
+		pr_warn("map '%s': can't use BPF map w/o FD (did you load it?)\n", map->name);
 		return -EINVAL;
+	}
 
 	st_ops_link = container_of(link, struct bpf_link_struct_ops, link);
 	/* Ensure the type of a link is correct */