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

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

[Simon Horman]

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@kernel.org>
Signed-off-by: Simon Horman <horms@kernel.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;
 }

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

[Simon Horman]

On Thu, Aug 01, 2024 at 07:35:37PM +0100, Simon Horman wrote:
> 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@kernel.org>
> Signed-off-by: Simon Horman <horms@kernel.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

Just to clarify. The formatting issue I was referring, is a double space
in the subject [1], which seems to of occurred due to the subject being
linewrapped and then unlinewrapped. However, in the light of a new day,
it is not at all clear to me that b4 is the cause of the problem.
So sorry for pointing my finger at it.

[1] https://lore.kernel.org/netdev/20240731182356.01a4c2b8@kernel.org/

> - Added Acked-by tag from Jakub
> - Link to v1: https://lore.kernel.org/r/20240731-tipic-overrun-v1-1-32ce5098c3e9@kernel.org

...

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

[patchwork-bot+netdevbpf]

Hello:

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

On Thu, 01 Aug 2024 19:35:37 +0100 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [net-next,v2] tipc: guard against string buffer overrun
    https://git.kernel.org/netdev/net-next/c/6555a2a9212b

You are awesome, thank you!
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