6.6-stable review patch. If anyone has any objections, please let me know.
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From: Mike Baynton mike@mbaynton.com
commit 6c4a5f96450415735c31ed70ff354f0ee5cbf67b upstream.
Some overlayfs features require permission to read/write trusted.* xattrs. These include redirect_dir, verity, metacopy, and data-only layers. This patch adds additional validations at mount time to stop overlays from mounting in certain cases where the resulting mount would not function according to the user's expectations because they lack permission to access trusted.* xattrs (for example, not global root.)
Similar checks in ovl_make_workdir() that disable features instead of failing are still relevant and used in cases where the resulting mount can still work "reasonably well." Generally, if the feature was enabled through kernel config or module option, any mount that worked before will still work the same; this applies to redirect_dir and metacopy. The user must explicitly request these features in order to generate a mount failure. Verity and data-only layers on the other hand must be explictly requested and have no "reasonable" disabled or degraded alternative, so mounts attempting either always fail.
"lower data-only dirs require metacopy support" moved down in case userxattr is set, which disables metacopy.
Cc: stable@vger.kernel.org # v6.6+ Signed-off-by: Mike Baynton mike@mbaynton.com Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/overlayfs/params.c | 38 +++++++++++++++++++++++++++++++++----- 1 file changed, 33 insertions(+), 5 deletions(-)
--- a/fs/overlayfs/params.c +++ b/fs/overlayfs/params.c @@ -761,11 +761,6 @@ int ovl_fs_params_verify(const struct ov { struct ovl_opt_set set = ctx->set;
- if (ctx->nr_data > 0 && !config->metacopy) { - pr_err("lower data-only dirs require metacopy support.\n"); - return -EINVAL; - } - /* Workdir/index are useless in non-upper mount */ if (!config->upperdir) { if (config->workdir) { @@ -917,6 +912,39 @@ int ovl_fs_params_verify(const struct ov config->metacopy = false; }
+ /* + * Fail if we don't have trusted xattr capability and a feature was + * explicitly requested that requires them. + */ + if (!config->userxattr && !capable(CAP_SYS_ADMIN)) { + if (set.redirect && + config->redirect_mode != OVL_REDIRECT_NOFOLLOW) { + pr_err("redirect_dir requires permission to access trusted xattrs\n"); + return -EPERM; + } + if (config->metacopy && set.metacopy) { + pr_err("metacopy requires permission to access trusted xattrs\n"); + return -EPERM; + } + if (config->verity_mode) { + pr_err("verity requires permission to access trusted xattrs\n"); + return -EPERM; + } + if (ctx->nr_data > 0) { + pr_err("lower data-only dirs require permission to access trusted xattrs\n"); + return -EPERM; + } + /* + * Other xattr-dependent features should be disabled without + * great disturbance to the user in ovl_make_workdir(). + */ + } + + if (ctx->nr_data > 0 && !config->metacopy) { + pr_err("lower data-only dirs require metacopy support.\n"); + return -EINVAL; + } + return 0; }