The kzmalloc call in bpf_check can fail when memory is very fragmented,
which in turn can lead to an OOM kill.

Use kvzmalloc to fall back to vmalloc when memory is too fragmented to
allocate an order 3 sized bpf verifier environment.

Admittedly this is not a very common case, and only happens on systems
where memory has already been squeezed close to the limit, but this does
not seem like much of a hot path, and it's a simple enough fix.

Signed-off-by: Rik van Riel <riel@surriel.com>
---
 kernel/bpf/verifier.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index dd86282ccaa4..0c41646a8793 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -22298,7 +22298,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 	/* 'struct bpf_verifier_env' can be global, but since it's not small,
 	 * allocate/free it every time bpf_check() is called
 	 */
-	env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL);
+	env = kvzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL);
 	if (!env)
 		return -ENOMEM;
 
@@ -22534,6 +22534,6 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 		mutex_unlock(&bpf_verifier_lock);
 	vfree(env->insn_aux_data);
 err_free_env:
-	kfree(env);
+	kvfree(env);
 	return ret;
 }
-- 
2.45.2

On Tue, Oct 08, 2024 at 05:07:35PM GMT, Rik van Riel wrote:
> The kzmalloc call in bpf_check can fail when memory is very fragmented,
> which in turn can lead to an OOM kill.
> 
> Use kvzmalloc to fall back to vmalloc when memory is too fragmented to
> allocate an order 3 sized bpf verifier environment.
> 
> Admittedly this is not a very common case, and only happens on systems
> where memory has already been squeezed close to the limit, but this does
> not seem like much of a hot path, and it's a simple enough fix.
> 
> Signed-off-by: Rik van Riel <riel@surriel.com>

It seems like a temporary allocation, so using kvmalloc* seems
reasonable.

Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>