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

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Message-ID: <20250503043050.861238-1-dw@davidwei.uk>
Date: Fri,  2 May 2025 21:30:50 -0700
From: David Wei <dw@...idwei.uk>
To: netdev@...r.kernel.org
Cc: Donald Hunter <donald.hunter@...il.com>,
	Jakub Kicinski <kuba@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Jacob Keller <jacob.e.keller@...el.com>
Subject: [PATCH net-next v1] tools: ynl-gen: validate 0 len strings from kernel

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@...idwei.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