[PATCH bpf] bpf: fix potential error return

[PATCH bpf] bpf: fix potential error return

[Anton Protopopov]

The bpf_remove_insns() function returns WARN_ON_ONCE(error), where
error is a result of bpf_adj_branches(), and thus should be always 0
However, if for any reason it is not 0, then it will be converted to
boolean by WARN_ON_ONCE and returned to user space as 1, not an actual
error value. Fix this by returning the original err after the WARN check.

Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
---
 kernel/bpf/core.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index a2327c4fdc8b..8b9711e6da6c 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -539,6 +539,8 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
 
 int bpf_remove_insns(struct bpf_prog *prog, u32 off, u32 cnt)
 {
+	int err;
+
 	/* Branch offsets can't overflow when program is shrinking, no need
 	 * to call bpf_adj_branches(..., true) here
 	 */
@@ -546,7 +548,9 @@ int bpf_remove_insns(struct bpf_prog *prog, u32 off, u32 cnt)
 		sizeof(struct bpf_insn) * (prog->len - off - cnt));
 	prog->len -= cnt;
 
-	return WARN_ON_ONCE(bpf_adj_branches(prog, off, off + cnt, off, false));
+	err = bpf_adj_branches(prog, off, off + cnt, off, false);
+	WARN_ON_ONCE(err);
+	return err;
 }
 
 static void bpf_prog_kallsyms_del_subprogs(struct bpf_prog *fp)
-- 
2.34.1

Re: [PATCH bpf] bpf: fix potential error return

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Tue, 10 Dec 2024 11:42:45 +0000 you wrote:
> The bpf_remove_insns() function returns WARN_ON_ONCE(error), where
> error is a result of bpf_adj_branches(), and thus should be always 0
> However, if for any reason it is not 0, then it will be converted to
> boolean by WARN_ON_ONCE and returned to user space as 1, not an actual
> error value. Fix this by returning the original err after the WARN check.
> 
> Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
> Acked-by: Jiri Olsa <jolsa@kernel.org>
> Acked-by: Andrii Nakryiko <andrii@kernel.org>
> 
> [...]

Here is the summary with links:
  - [bpf] bpf: fix potential error return
    https://git.kernel.org/bpf/bpf/c/c4441ca86afe

You are awesome, thank you!
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