diff mbox series

[bpf,v2,1/2] bpf: Resolve fext program type when checking map compatibility

Message ID 20221209142622.154126-1-toke@redhat.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series [bpf,v2,1/2] bpf: Resolve fext program type when checking map compatibility | expand

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bpf/vmtest-bpf-VM_Test-16 success Logs for test_progs on s390x with gcc
bpf/vmtest-bpf-VM_Test-21 success Logs for test_progs_no_alu32 on s390x with gcc
bpf/vmtest-bpf-VM_Test-26 success Logs for test_progs_no_alu32_parallel on s390x with gcc
bpf/vmtest-bpf-VM_Test-31 success Logs for test_progs_parallel on s390x with gcc
netdev/tree_selection success Clearly marked for bpf, async
netdev/fixes_present success Fixes tag present in non-next series
netdev/subject_prefix success Link
netdev/cover_letter success Single patches do not need cover letters
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 53 this patch: 53
netdev/cc_maintainers success CCed 14 of 14 maintainers
netdev/build_clang success Errors and warnings before: 17 this patch: 17
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/check_selftest success No net selftest shell script
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Commit Message

Toke Høiland-Jørgensen Dec. 9, 2022, 2:26 p.m. UTC
The bpf_prog_map_compatible() check makes sure that BPF program types are
not mixed inside BPF map types that can contain programs (tail call maps,
cpumaps and devmaps). It does this by setting the fields of the map->owner
struct to the values of the first program being checked against, and
rejecting any subsequent programs if the values don't match.

One of the values being set in the map owner struct is the program type,
and since the code did not resolve the prog type for fext programs, the map
owner type would be set to PROG_TYPE_EXT and subsequent loading of programs
of the target type into the map would fail.

This bug is seen in particular for XDP programs that are loaded as
PROG_TYPE_EXT using libxdp; these cannot insert programs into devmaps and
cpumaps because the check fails as described above.

Fix the bug by resolving the fext program type to its target program type
as elsewhere in the verifier. This requires constifying the parameter of
resolve_prog_type() to avoid a compiler warning from the new call site.

Fixes: f45d5b6ce2e8 ("bpf: generalise tail call map compatibility check")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
No changes since v1, this just adds a selftest (in patch 2).

 include/linux/bpf_verifier.h | 2 +-
 kernel/bpf/core.c            | 5 +++--
 2 files changed, 4 insertions(+), 3 deletions(-)

Comments

Yonghong Song Dec. 9, 2022, 5:36 p.m. UTC | #1
On 12/9/22 6:26 AM, Toke Høiland-Jørgensen wrote:
> The bpf_prog_map_compatible() check makes sure that BPF program types are
> not mixed inside BPF map types that can contain programs (tail call maps,
> cpumaps and devmaps). It does this by setting the fields of the map->owner
> struct to the values of the first program being checked against, and
> rejecting any subsequent programs if the values don't match.
> 
> One of the values being set in the map owner struct is the program type,
> and since the code did not resolve the prog type for fext programs, the map
> owner type would be set to PROG_TYPE_EXT and subsequent loading of programs
> of the target type into the map would fail.
> 
> This bug is seen in particular for XDP programs that are loaded as
> PROG_TYPE_EXT using libxdp; these cannot insert programs into devmaps and
> cpumaps because the check fails as described above.
> 
> Fix the bug by resolving the fext program type to its target program type
> as elsewhere in the verifier. This requires constifying the parameter of
> resolve_prog_type() to avoid a compiler warning from the new call site.
> 
> Fixes: f45d5b6ce2e8 ("bpf: generalise tail call map compatibility check")
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>

Acked-by: Yonghong Song <yhs@fb.com>
diff mbox series

Patch

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 9e1e6965f407..0eb8f035b3d9 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -642,7 +642,7 @@  static inline u32 type_flag(u32 type)
 }
 
 /* only use after check_attach_btf_id() */
-static inline enum bpf_prog_type resolve_prog_type(struct bpf_prog *prog)
+static inline enum bpf_prog_type resolve_prog_type(const struct bpf_prog *prog)
 {
 	return prog->type == BPF_PROG_TYPE_EXT ?
 		prog->aux->dst_prog->type : prog->type;
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 25a54e04560e..17ab3e15ac25 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2088,6 +2088,7 @@  static unsigned int __bpf_prog_ret0_warn(const void *ctx,
 bool bpf_prog_map_compatible(struct bpf_map *map,
 			     const struct bpf_prog *fp)
 {
+	enum bpf_prog_type prog_type = resolve_prog_type(fp);
 	bool ret;
 
 	if (fp->kprobe_override)
@@ -2098,12 +2099,12 @@  bool bpf_prog_map_compatible(struct bpf_map *map,
 		/* There's no owner yet where we could check for
 		 * compatibility.
 		 */
-		map->owner.type  = fp->type;
+		map->owner.type  = prog_type;
 		map->owner.jited = fp->jited;
 		map->owner.xdp_has_frags = fp->aux->xdp_has_frags;
 		ret = true;
 	} else {
-		ret = map->owner.type  == fp->type &&
+		ret = map->owner.type  == prog_type &&
 		      map->owner.jited == fp->jited &&
 		      map->owner.xdp_has_frags == fp->aux->xdp_has_frags;
 	}