diff options
| author | Richard Weinberger <richard@nod.at> | 2016-09-16 11:45:24 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-10-28 03:01:30 -0400 |
| commit | 0a5600d83fa5a251c91459779d5311a005e4c5b3 (patch) | |
| tree | fdb05eeb394ef3dbd0cda4dbdc57f8105e87103f /fs/overlayfs | |
| parent | 2add76a428bc6b9e4506d9caa4f8ced9b8bdcb70 (diff) | |
ovl: Fix info leak in ovl_lookup_temp()
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 <richard@nod.at>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: e9be9d5e76e3 ("overlay filesystem")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/overlayfs')
| -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 ba5ef733951f..327177df03a5 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -12,6 +12,7 @@ #include <linux/xattr.h> #include <linux/security.h> #include <linux/cred.h> +#include <linux/atomic.h> #include "overlayfs.h" void ovl_cleanup(struct inode *wdir, struct dentry *wdentry) @@ -35,8 +36,10 @@ 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) { |