[PATCH] jfs: Use unsigned variable for length calculations

Kees Cook
2023-02-04T18:34:03Z

To avoid confusing the compiler about possible negative sizes, switch
"ssize" which can never be negative from int to u32. Seen with GCC 13:

../fs/jfs/namei.c: In function 'jfs_symlink': ../include/linux/fortify-string.h:57:33: warning: '__builtin_memcpy' pointer overflow between offset 0 and size [-2147483648, -1]
[-Warray-bounds=]
57 | #define __underlying_memcpy __builtin_memcpy
| ^
...
../fs/jfs/namei.c:950:17: note: in expansion of macro 'memcpy'
950 | memcpy(ip->i_link, name, ssize);
| ^~~~~~

Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: jfs-discussion@lists.sourceforge.net
Signed-off-by: Kees Cook <keescook@chromium.org>
---
fs/jfs/namei.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c
index b29d68b5eec5..494b9f4043cf 100644
--- a/fs/jfs/namei.c
+++ b/fs/jfs/namei.c
@@ -876,7 +876,7 @@ static int jfs_symlink(struct mnt_idmap *idmap, struct inode *dip,
tid_t tid;
ino_t ino = 0;
struct component_name dname;
- int ssize; /* source pathname size */
+ u32 ssize; /* source pathname size */
struct btstack btstack;
struct inode *ip = d_inode(dentry);
s64 xlen = 0;
@@ -957,7 +957,7 @@ static int jfs_symlink(struct mnt_idmap *idmap, struct inode *dip,
if (ssize > sizeof (JFS_IP(ip)->i_inline))
JFS_IP(ip)->mode2 &= ~INLINEEA;

- jfs_info("jfs_symlink: fast symlink added ssize:%d name:%s ",
+ jfs_info("jfs_symlink: fast symlink added ssize:%u name:%s ",
ssize, name);
}
/*
@@ -987,7 +987,7 @@ static int jfs_symlink(struct mnt_idmap *idmap, struct inode *dip,
ip->i_size = ssize - 1;
while (ssize) {
/* This is kind of silly since PATH_MAX == 4K */
- int copy_size = min(ssize, PSIZE);
+ u32 copy_size = min_t(u32, ssize, PSIZE);

mp = get_metapage(ip, xaddr, PSIZE, 1);

--
2.34.1