The patch titled
NFS: Replace null dentries that appear in readdir's list
has been removed from the -mm tree. Its filename is
nfs-replace-null-dentries-that-appear-in-readdirs-list.patch
This patch was dropped because an updated version was merged
------------------------------------------------------
Subject: NFS: Replace null dentries that appear in readdir's list
From: David Howells <dhowells@xxxxxxxxxx>
Have nfs_readdir_lookup() drop and replace any null dentry when it
that gets listed by a READDIR RPC call.
This can be caused by an optimisation in nfs_lookup() that causes a dentry to
be incorrectly left as negative when mkdir() or similar is aborted by SELinux
mid-procedure.
This can be triggered by mounting through autofs4 a server:/ NFS share for
which there are other exports available on that server. SELinux also has to
be turned on in enforcing mode to abort mid-flow the mkdir operation performed
by autofs4.
The problematic sequence of events is this:
(1) nfs_lookup() is called by sys_mkdirat() -> lookup_create() ->
__lookup_hash() with intent to create exclusively set in the nameidata:
nd->flags == LOOKUP_CREATE
nd->intent.open.flags == O_EXCL
(2) nfs_lookup() has an optimisation to avoid going to the server in this
case, presumably since the nfs_mkdir() op or whatever will deal with the
conflict.
(3) nfs_lookup() returns successfully, leaving the dentry in a negative state,
but attached to the parent directory.
(4) sys_mkdirat() calls vfs_mkdir() which calls may_create(). may_create()
checks that the directory has MAY_WRITE and MAY_EXEC permissions.
(5) may_create() calls nfs_permission(), which grants permission.
(6) may_create() calls security_inode_permission(), which calls SELinux, which
then _DENIES_ permission.
(7) may_create() fails, and vfs_mkdir() then fails and sys_mkdirat() then
fails (as does sys_mkdir).
_However_, the new dentry is left in the negative state, with no
consultation of the server.
(8) The parent directory is listed, and the name of the new dentry is
returned.
(9) stat on the new dentry fails (because it's negative), and "ls -l" returns
"?---------" as the file type and mode.
This fix makes step (8) replace the dentry looked up in steps (1) - (3).
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
fs/nfs/dir.c | 9 +++++++--
1 files changed, 7 insertions(+), 2 deletions(-)
diff -puN fs/nfs/dir.c~nfs-replace-null-dentries-that-appear-in-readdirs-list fs/nfs/dir.c
--- a/fs/nfs/dir.c~nfs-replace-null-dentries-that-appear-in-readdirs-list
+++ a/fs/nfs/dir.c
@@ -1105,8 +1105,13 @@ static struct dentry *nfs_readdir_lookup
}
name.hash = full_name_hash(name.name, name.len);
dentry = d_lookup(parent, &name);
- if (dentry != NULL)
- return dentry;
+ if (dentry != NULL) {
+ /* negative dentries must be reconsidered */
+ if (!IS_ERR(dentry) && !dentry->d_inode)
+ d_drop(dentry);
+ else
+ return dentry;
+ }
if (!desc->plus || !(entry->fattr->valid & NFS_ATTR_FATTR))
return NULL;
/* Note: caller is already holding the dir->i_mutex! */
_
Patches currently in -mm which might be from dhowells@xxxxxxxxxx are
git-gfs2.patch
git-nfs.patch
nfs-replace-null-dentries-that-appear-in-readdirs-list.patch
binfmt_elf-consistently-use-loff_t.patch
afs-add-lock-annotations-to-afs_proc_cell_servers_startstop.patch
elf_fdpic_core_dump-dont-take-tasklist_lock.patch
reiserfs-make-sure-all-dentries-refs-are-released-before-calling-kill_block_super-try-2.patch
fs-cache-provide-a-filesystem-specific-syncable-page-bit.patch
fs-cache-generic-filesystem-caching-facility.patch
fs-cache-release-page-private-in-failed-readahead.patch
fs-cache-make-kafs-use-fs-cache.patch
fs-cache-make-kafs-use-fs-cache-fix.patch
fs-cache-make-kafs-use-fs-cache-vs-streamline-generic_file_-interfaces-and-filemap.patch
nfs-use-local-caching.patch
fs-cache-cachefiles-ia64-missing-copy_page-export.patch
fs-cache-cachefiles-a-cache-that-backs-onto-a-mounted-filesystem.patch
fs-cache-cachefiles-a-cache-that-backs-onto-a-mounted-filesystem-cachefiles-printk-format-warning.patch
autofs-make-sure-all-dentries-refs-are-released-before-calling-kill_anon_super.patch
vfs-destroy-the-dentries-contributed-by-a-superblock-on-unmounting.patch
vfs-make-filldir_t-and-struct-kstat-deal-in-64-bit-inode-numbers.patch
nfs-represent-64-bit-fileids-as-64-bit-inode-numbers-on-32-bit-systems.patch
ecryptfs-get_sb_dev-fix.patch
reiser4-get_sb_dev-fix.patch
mutex-subsystem-synchro-test-module.patch
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