netdev - [PATCH net-next v2] tipc: guard against string buffer overrun

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Message-Id: <20240801-tipic-overrun-v2-1-c5b869d1f074@kernel.org>
Date: Thu, 01 Aug 2024 19:35:37 +0100
From: Simon Horman <horms@...nel.org>
To: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>
Cc: Jon Maloy <jmaloy@...hat.com>, Ying Xue <ying.xue@...driver.com>, 
 Per Liden <per.liden@...pam.ericsson.com>, netdev@...r.kernel.org, 
 tipc-discussion@...ts.sourceforge.net
Subject: [PATCH net-next v2] tipc: guard against string buffer overrun

Smatch reports that copying media_name and if_name to name_parts may
overwrite the destination.

 .../bearer.c:166 bearer_name_validate() error: strcpy() 'media_name' too large for 'name_parts->media_name' (32 vs 16)
 .../bearer.c:167 bearer_name_validate() error: strcpy() 'if_name' too large for 'name_parts->if_name' (1010102 vs 16)

This does seem to be the case so guard against this possibility by using
strscpy() and failing if truncation occurs.

Introduced by commit b97bf3fd8f6a ("[TIPC] Initial merge")

Compile tested only.

Reviewed-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Simon Horman <horms@...nel.org>
---
I am not marking this as a fix for net as I am not aware of this
actually breaking anything in practice. Thus, at this point I consider
it more of a clean-up than a bug fix.
---
Changes in v2:
- Correct formatting and typo in subject (Thanks Jakub)
  + The formatting problem was caused by tooling (b4)
    so I reworded the subject as a work-around
- Added Acked-by tag from Jakub
- Link to v1: https://lore.kernel.org/r/20240731-tipic-overrun-v1-1-32ce5098c3e9@kernel.org
---
 net/tipc/bearer.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index 5a526ebafeb4..3c9e25f6a1d2 100644
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -163,8 +163,12 @@ static int bearer_name_validate(const char *name,

 	/* return bearer name components, if necessary */
 	if (name_parts) {
-		strcpy(name_parts->media_name, media_name);
-		strcpy(name_parts->if_name, if_name);
+		if (strscpy(name_parts->media_name, media_name,
+			    TIPC_MAX_MEDIA_NAME) < 0)
+			return 0;
+		if (strscpy(name_parts->if_name, if_name,
+			    TIPC_MAX_IF_NAME) < 0)
+			return 0;
 	}
 	return 1;
 }