4.8-stable review patch. If anyone has any objections, please let me know.
------------------ From: Richard Weinberger <[email protected]> commit 6a45b3628ce4dcf7498b39c87d475bab6e2a9b24 upstream. The function uses the memory address of a struct dentry as unique id. While the address-based directory entry is only visible to root it is IMHO still worth fixing since the temporary name does not have to be a kernel address. It can be any unique number. Replace it by an atomic integer which is allowed to wrap around. Signed-off-by: Richard Weinberger <[email protected]> Reviewed-by: Kees Cook <[email protected]> Signed-off-by: Miklos Szeredi <[email protected]> Fixes: e9be9d5e76e3 ("overlay filesystem") Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/overlayfs/dir.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -14,6 +14,7 @@ #include <linux/cred.h> #include <linux/posix_acl.h> #include <linux/posix_acl_xattr.h> +#include <linux/atomic.h> #include "overlayfs.h" void ovl_cleanup(struct inode *wdir, struct dentry *wdentry) @@ -37,8 +38,10 @@ struct dentry *ovl_lookup_temp(struct de { struct dentry *temp; char name[20]; + static atomic_t temp_id = ATOMIC_INIT(0); - snprintf(name, sizeof(name), "#%lx", (unsigned long) dentry); + /* counter is allowed to wrap, since temp dentries are ephemeral */ + snprintf(name, sizeof(name), "#%x", atomic_inc_return(&temp_id)); temp = lookup_one_len(name, workdir, strlen(name)); if (!IS_ERR(temp) && temp->d_inode) {
