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| author |   NeilBrown <neilb@suse.de> | 2022-08-19 09:55:59 +1000 |
|---|---|---|
| committer |   Trond Myklebust <trond.myklebust@hammerspace.com> | 2022-08-19 20:31:36 -0400 |
| commit | f16857e62bac60786104c020ad7c86e2163b2c5b (patch) | |
| tree | 1f34d39d7ebcd810007bfc6bb304289ab0857fa6 /fs/nfs | |
| parent | NFS: Cleanup to remove unused flag NFS_CONTEXT_RESEND_WRITES (diff) | |
| download | linux-dev-f16857e62bac60786104c020ad7c86e2163b2c5b.tar.xz linux-dev-f16857e62bac60786104c020ad7c86e2163b2c5b.zip | |
NFS: unlink/rmdir shouldn't call d_delete() twice on ENOENT
nfs_unlink() calls d_delete() twice if it receives ENOENT from the
server - once in nfs_dentry_handle_enoent() from nfs_safe_remove and
once in nfs_dentry_remove_handle_error().
nfs_rmddir() also calls it twice - the nfs_dentry_handle_enoent() call
is direct and inside a region locked with ->rmdir_sem
It is safe to call d_delete() twice if the refcount > 1 as the dentry is
simply unhashed.
If the refcount is 1, the first call sets d_inode to NULL and the second
call crashes.
This patch guards the d_delete() call from nfs_dentry_handle_enoent()
leaving the one under ->remdir_sem in case that is important.
In mainline it would be safe to remove the d_delete() call. However in
older kernels to which this might be backported, that would change the
behaviour of nfs_unlink(). nfs_unlink() used to unhash the dentry which
resulted in nfs_dentry_handle_enoent() not calling d_delete(). So in
older kernels we need the d_delete() in nfs_dentry_remove_handle_error()
when called from nfs_unlink() but not when called from nfs_rmdir().
To make the code work correctly for old and new kernels, and from both
nfs_unlink() and nfs_rmdir(), we protect the d_delete() call with
simple_positive(). This ensures it is never called in a circumstance
where it could crash.
Fixes: 3c59366c207e ("NFS: don't unhash dentry during unlink/rename")
Fixes: 9019fb391de0 ("NFS: Label the dentry with a verifier in nfs_rmdir() and nfs_unlink()")
Signed-off-by: NeilBrown <neilb@suse.de>
Tested-by: Olga Kornievskaia <aglo@umich.edu>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Diffstat (limited to 'fs/nfs')
| -rw-r--r-- | fs/nfs/dir.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index 1b879584d4fe..5d6c2ddc7ea6 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -2382,7 +2382,8 @@ static void nfs_dentry_remove_handle_error(struct inode *dir, { switch (error) { case -ENOENT: - d_delete(dentry); + if (d_really_is_positive(dentry)) + d_delete(dentry); nfs_set_verifier(dentry, nfs_save_change_attribute(dir)); break; case 0: |