diff options
| author | Richard Weinberger <richard@nod.at> | 2016-09-16 11:45:24 +0200 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2016-09-21 16:37:07 +0200 |
| commit | 6a45b3628ce4dcf7498b39c87d475bab6e2a9b24 (patch) | |
| tree | fb203edbc99e09b1c34be42f203704a651530ddf /fs/overlayfs/dir.c | |
| parent | 8eac98b8beb4711c4ab61822cac077fd6660e820 (diff) | |
ovl: Fix info leak in ovl_lookup_temp()
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 <richard@nod.at>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org> # v3.18+
Fixes: e9be9d5e76e3 ("overlay filesystem")
Diffstat (limited to 'fs/overlayfs/dir.c')
| -rw-r--r-- | fs/overlayfs/dir.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c index 1560fdc09a5f..74e696426aae 100644 --- 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 dentry *workdir, struct dentry *dentry) { 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) { |