[PATCH net-next v1] tools: ynl-gen: validate 0 len strings from kernel

[PATCH net-next v1] tools: ynl-gen: validate 0 len strings from kernel

[David Wei]

Strings from the kernel are guaranteed to be null terminated and
ynl_attr_validate() checks for this. But it doesn't check if the string
has a len of 0, which would cause problems when trying to access
data[len - 1]. Fix this by checking that len is positive.

Signed-off-by: David Wei <dw@davidwei.uk>
---
 tools/net/ynl/lib/ynl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/net/ynl/lib/ynl.c b/tools/net/ynl/lib/ynl.c
index d263f6f40ad5..a0b54ad4c073 100644
--- a/tools/net/ynl/lib/ynl.c
+++ b/tools/net/ynl/lib/ynl.c
@@ -364,7 +364,7 @@ int ynl_attr_validate(struct ynl_parse_arg *yarg, const struct nlattr *attr)
 		     "Invalid attribute (binary %s)", policy->name);
 		return -1;
 	case YNL_PT_NUL_STR:
-		if ((!policy->len || len <= policy->len) && !data[len - 1])
+		if (len && (!policy->len || len <= policy->len) && !data[len - 1])
 			break;
 		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
 		     "Invalid attribute (string %s)", policy->name);
-- 
2.47.1

Re: [PATCH net-next v1] tools: ynl-gen: validate 0 len strings from kernel

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri,  2 May 2025 21:30:50 -0700 you wrote:
> Strings from the kernel are guaranteed to be null terminated and
> ynl_attr_validate() checks for this. But it doesn't check if the string
> has a len of 0, which would cause problems when trying to access
> data[len - 1]. Fix this by checking that len is positive.
> 
> Signed-off-by: David Wei <dw@davidwei.uk>
> 
> [...]

Here is the summary with links:
  - [net-next,v1] tools: ynl-gen: validate 0 len strings from kernel
    https://git.kernel.org/netdev/net/c/4720f9707c78

You are awesome, thank you!
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