[PATCH 6.6 087/267] landlock: Fix d_parent walk

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



6.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mickaël Salaün <mic@xxxxxxxxxxx>

commit 88da52ccd66e65f2e63a6c35c9dff55d448ef4dc upstream.

The WARN_ON_ONCE() in collect_domain_accesses() can be triggered when
trying to link a root mount point.  This cannot work in practice because
this directory is mounted, but the VFS check is done after the call to
security_path_link().

Do not use source directory's d_parent when the source directory is the
mount point.

Cc: Günther Noack <gnoack@xxxxxxxxxx>
Cc: Paul Moore <paul@xxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: syzbot+bf4903dc7e12b18ebc87@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: b91c3e4ea756 ("landlock: Add support for file reparenting with LANDLOCK_ACCESS_FS_REFER")
Closes: https://lore.kernel.org/r/000000000000553d3f0618198200@xxxxxxxxxx
Link: https://lore.kernel.org/r/20240516181935.1645983-2-mic@xxxxxxxxxxx
[mic: Fix commit message]
Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 security/landlock/fs.c |   13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -820,6 +820,7 @@ static int current_check_refer_path(stru
 	bool allow_parent1, allow_parent2;
 	access_mask_t access_request_parent1, access_request_parent2;
 	struct path mnt_dir;
+	struct dentry *old_parent;
 	layer_mask_t layer_masks_parent1[LANDLOCK_NUM_ACCESS_FS] = {},
 		     layer_masks_parent2[LANDLOCK_NUM_ACCESS_FS] = {};
 
@@ -867,9 +868,17 @@ static int current_check_refer_path(stru
 	mnt_dir.mnt = new_dir->mnt;
 	mnt_dir.dentry = new_dir->mnt->mnt_root;
 
+	/*
+	 * old_dentry may be the root of the common mount point and
+	 * !IS_ROOT(old_dentry) at the same time (e.g. with open_tree() and
+	 * OPEN_TREE_CLONE).  We do not need to call dget(old_parent) because
+	 * we keep a reference to old_dentry.
+	 */
+	old_parent = (old_dentry == mnt_dir.dentry) ? old_dentry :
+						      old_dentry->d_parent;
+
 	/* new_dir->dentry is equal to new_dentry->d_parent */
-	allow_parent1 = collect_domain_accesses(dom, mnt_dir.dentry,
-						old_dentry->d_parent,
+	allow_parent1 = collect_domain_accesses(dom, mnt_dir.dentry, old_parent,
 						&layer_masks_parent1);
 	allow_parent2 = collect_domain_accesses(
 		dom, mnt_dir.dentry, new_dir->dentry, &layer_masks_parent2);






[Index of Archives]     [Linux Kernel]     [Kernel Development Newbies]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Hiking]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux