Re: [PATCH] jfs: Use unsigned variable for length calculations

Dr. David Alan Gilbert
2023-02-04T20:26:11Z

* Kees Cook (keescook@chromium.org) wrote:
> 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 */

Had you considered using size_t - this is set from a strlen and used by a memcpy
that both talk size_t.

Dave

> 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
>
--
-----Open up your eyes, open up your mind, open up your code -------
/ Dr. David Alan Gilbert | Running GNU/Linux | Happy \
\ dave @ treblig.org | | In Hex /
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