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| author | Miklos Szeredi <mszeredi@redhat.com> | 2020-12-14 15:26:14 +0100 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2020-12-14 15:26:14 +0100 |
| commit | c846af050f944d584f28bc0de310383003c8096d (patch) | |
| tree | 32070dcfc93dd4164928c5d7056836f5c420bfc7 | |
| parent | 3078d85c9a1099405a0463c4d112ba97ee5bd217 (diff) | |
| download | linux-c846af050f944d584f28bc0de310383003c8096d.tar.gz linux-c846af050f944d584f28bc0de310383003c8096d.tar.bz2 linux-c846af050f944d584f28bc0de310383003c8096d.zip | |
ovl: check privs before decoding file handle
CAP_DAC_READ_SEARCH is required by open_by_handle_at(2) so check it in
ovl_decode_real_fh() as well to prevent privilege escalation for
unprivileged overlay mounts.
[Amir] If the mounter is not capable in init ns, ovl_check_origin() and
ovl_verify_index() will not function as expected and this will break index
and nfs export features. So check capability in ovl_can_decode_fh(), to
auto disable those features.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
| -rw-r--r-- | fs/overlayfs/namei.c | 3 | ||||
| -rw-r--r-- | fs/overlayfs/util.c | 3 |
2 files changed, 6 insertions, 0 deletions
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c index 509dac77af61..3fe05fb5d145 100644 --- a/fs/overlayfs/namei.c +++ b/fs/overlayfs/namei.c @@ -156,6 +156,9 @@ struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh, struct dentry *real; int bytes; + if (!capable(CAP_DAC_READ_SEARCH)) + return NULL; + /* * Make sure that the stored uuid matches the uuid of the lower * layer where file handle will be decoded. diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c index 44b4b62a8ac8..ced63c79e9dd 100644 --- a/fs/overlayfs/util.c +++ b/fs/overlayfs/util.c @@ -50,6 +50,9 @@ const struct cred *ovl_override_creds(struct super_block *sb) */ int ovl_can_decode_fh(struct super_block *sb) { + if (!capable(CAP_DAC_READ_SEARCH)) + return 0; + if (!sb->s_export_op || !sb->s_export_op->fh_to_dentry) return 0; |