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vfs, security: Fix automount superblock LSM init problem, preventing NFS sb sharing

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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 <dhowells@redhat.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
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: 9bc61ab18b ("vfs: Introduce fs_context, switch vfs_kern_mount() to it.")
Fixes: 779df6a548 ("NFS: Ensure security label is set for root inode")
Tested-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: "Christian Brauner (Microsoft)" <brauner@kernel.org>
Acked-by: Paul Moore <paul@paul-moore.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Message-Id: <20230808-master-v9-1-e0ecde888221@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
David Howells
2023-08-08 07:34:20 -04:00
committed by Christian Brauner
parent 4352b8cd66
commit d80a8f1b58
6 changed files with 116 additions and 1 deletions
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23
fs/fs_context.c
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@@ -315,10 +315,31 @@ struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
}
EXPORT_SYMBOL(fs_context_for_reconfigure);
/**
* fs_context_for_submount: allocate a new fs_context for a submount
* @type: file_system_type of the new context
* @reference: reference dentry from which to copy relevant info
*
* Allocate a new fs_context suitable for a submount. This also ensures that
* the fc->security object is inherited from @reference (if needed).
*/
struct fs_context *fs_context_for_submount(struct file_system_type *type,
struct dentry *reference)
{
return alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT);
struct fs_context *fc;
int ret;
fc = alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT);
if (IS_ERR(fc))
return fc;
ret = security_fs_context_submount(fc, reference->d_sb);
if (ret) {
put_fs_context(fc);
return ERR_PTR(ret);
}
return fc;
}
EXPORT_SYMBOL(fs_context_for_submount);