2023-10-24 21:48:41

by Christophe JAILLET

Subject: [PATCH] NFS: Fix an off by one in root_nfs_cat()

The intent is to check if the 'dest' is truncated or not. So, >+ should be
used instead of >, because strlcat() returns the length of 'dest' and 'src'
excluding the trailing NULL.

Fixes: 56463e50d1fc ("NFS: Use super.c for NFSROOT mount option parsing")
Signed-off-by: Christophe JAILLET <[email protected]>
---
fs/nfs/nfsroot.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/nfsroot.c b/fs/nfs/nfsroot.c
index 7600100ba26f..432612d22437 100644
--- a/fs/nfs/nfsroot.c
+++ b/fs/nfs/nfsroot.c
@@ -175,10 +175,10 @@ static int __init root_nfs_cat(char *dest, const char *src,
size_t len = strlen(dest);

if (len && dest[len - 1] != ',')
- if (strlcat(dest, ",", destlen) > destlen)
+ if (strlcat(dest, ",", destlen) >= destlen)
return -1;

- if (strlcat(dest, src, destlen) > destlen)
+ if (strlcat(dest, src, destlen) >= destlen)
return -1;
return 0;
}
--
2.32.0

2023-10-25 12:36:00

by Benjamin Coddington

Subject: Re: [PATCH] NFS: Fix an off by one in root_nfs_cat()

On 24 Oct 2023, at 17:47, Christophe JAILLET wrote:

> The intent is to check if the 'dest' is truncated or not. So, >+ should be
> used instead of >, because strlcat() returns the length of 'dest' and 'src'
> excluding the trailing NULL.
>
> Fixes: 56463e50d1fc ("NFS: Use super.c for NFSROOT mount option parsing")
> Signed-off-by: Christophe JAILLET <[email protected]>

Minor typo in the body: >+ should be >=, otherwise looks right.

Reviewed-by: Benjamin Coddington <[email protected]>

Ben