| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.6 054/203] make nfs_atomic_open() call d_drop() on all ->open_context() errors. | Date | Mon, 25 Jul 2016 13:54:29 -0700 |
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4.6-stable review patch. If anyone has any objections, please let me know.
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From: Al Viro <viro@ZenIV.linux.org.uk>
commit d20cb71dbf3487f24549ede1a8e2d67579b4632e upstream.
In "NFSv4: Move dentry instantiation into the NFSv4-specific atomic open code" unconditional d_drop() after the ->open_context() had been removed. It had been correct for success cases (there ->open_context() itself had been doing dcache manipulations), but not for error ones. Only one of those (ENOENT) got a compensatory d_drop() added in that commit, but in fact it should've been done for all errors. As it is, the case of O_CREAT non-exclusive open on a hashed negative dentry racing with e.g. symlink creation from another client ended up with ->open_context() getting an error and proceeding to call nfs_lookup(). On a hashed dentry, which would've instantly triggered BUG_ON() in d_materialise_unique() (or, these days, its equivalent in d_splice_alias()).
Tested-by: Oleg Drokin <green@linuxhacker.ru> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- fs/nfs/dir.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -1527,9 +1527,9 @@ int nfs_atomic_open(struct inode *dir, s err = PTR_ERR(inode); trace_nfs_atomic_open_exit(dir, ctx, open_flags, err); put_nfs_open_context(ctx); + d_drop(dentry); switch (err) { case -ENOENT: - d_drop(dentry); d_add(dentry, NULL); nfs_set_verifier(dentry, nfs_save_change_attribute(dir)); break;
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