From d80a8f1b58c2bc8d7c6bfb65401ea4f7ec8cddc2 Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 8 Aug 2023 07:34:20 -0400 Subject: vfs, security: Fix automount superblock LSM init problem, preventing NFS sb sharing When NFS superblocks are created by automounting, their LSM parameters aren't set in the fs_context struct prior to sget_fc() being called, leading to failure to match existing superblocks. This bug leads to messages like the following appearing in dmesg when fscache is enabled: NFS: Cache volume key already in use (nfs,4.2,2,108,106a8c0,1,,,,100000,100000,2ee,3a98,1d4c,3a98,1) Fix this by adding a new LSM hook to load fc->security for submount creation. Signed-off-by: David Howells Signed-off-by: Jeff Layton Link: https://lore.kernel.org/r/165962680944.3334508.6610023900349142034.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/165962729225.3357250.14350728846471527137.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/165970659095.2812394.6868894171102318796.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/166133579016.3678898.6283195019480567275.stgit@warthog.procyon.org.uk/ # v4 Link: https://lore.kernel.org/r/217595.1662033775@warthog.procyon.org.uk/ # v5 Fixes: 9bc61ab18b1d ("vfs: Introduce fs_context, switch vfs_kern_mount() to it.") Fixes: 779df6a5480f ("NFS: Ensure security label is set for root inode") Tested-by: Jeff Layton Acked-by: Casey Schaufler Acked-by: "Christian Brauner (Microsoft)" Acked-by: Paul Moore Reviewed-by: Jeff Layton Message-Id: <20230808-master-v9-1-e0ecde888221@kernel.org> Signed-off-by: Christian Brauner --- security/security.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'security/security.c') diff --git a/security/security.c b/security/security.c index b720424ca37d..549104a447e3 100644 --- a/security/security.c +++ b/security/security.c @@ -1138,6 +1138,20 @@ void security_bprm_committed_creds(struct linux_binprm *bprm) call_void_hook(bprm_committed_creds, bprm); } +/** + * security_fs_context_submount() - Initialise fc->security + * @fc: new filesystem context + * @reference: dentry reference for submount/remount + * + * Fill out the ->security field for a new fs_context. + * + * Return: Returns 0 on success or negative error code on failure. + */ +int security_fs_context_submount(struct fs_context *fc, struct super_block *reference) +{ + return call_int_hook(fs_context_submount, 0, fc, reference); +} + /** * security_fs_context_dup() - Duplicate a fs_context LSM blob * @fc: destination filesystem context -- cgit v1.2.3