6.6-stable review patch. If anyone has any objections, please let me know.
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From: Paulo Alcantara pc@manguebit.org
[ Upstream commit 0af1561b2d60bab2a2b00720a5c7b292ecc549ec ]
According to some logs reported by customers, CIFS client might end up reporting unlinked files as existing in stat(2) due to concurrent opens racing with unlink(2).
Besides sending the removal request to the server, the unlink process could involve closing any deferred close as well as marking all existing open handles as deleted to prevent them from deferring closes, which increases the race window for potential concurrent opens.
Fix this by unhashing the dentry in cifs_unlink() to prevent any subsequent opens. Any open attempts, while we're still unlinking, will block on parent's i_rwsem.
Reported-by: Jay Shin jaeshin@redhat.com Signed-off-by: Paulo Alcantara (Red Hat) pc@manguebit.org Reviewed-by: David Howells dhowells@redhat.com Cc: Al Viro viro@zeniv.linux.org.uk Cc: linux-cifs@vger.kernel.org Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/smb/client/inode.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/fs/smb/client/inode.c b/fs/smb/client/inode.c index d93ebd58ecae1..df01029918fd4 100644 --- a/fs/smb/client/inode.c +++ b/fs/smb/client/inode.c @@ -1856,15 +1856,24 @@ int cifs_unlink(struct inode *dir, struct dentry *dentry) struct cifs_sb_info *cifs_sb = CIFS_SB(sb); struct tcon_link *tlink; struct cifs_tcon *tcon; + __u32 dosattr = 0, origattr = 0; struct TCP_Server_Info *server; struct iattr *attrs = NULL; - __u32 dosattr = 0, origattr = 0; + bool rehash = false;
cifs_dbg(FYI, "cifs_unlink, dir=0x%p, dentry=0x%p\n", dir, dentry);
if (unlikely(cifs_forced_shutdown(cifs_sb))) return -EIO;
+ /* Unhash dentry in advance to prevent any concurrent opens */ + spin_lock(&dentry->d_lock); + if (!d_unhashed(dentry)) { + __d_drop(dentry); + rehash = true; + } + spin_unlock(&dentry->d_lock); + tlink = cifs_sb_tlink(cifs_sb); if (IS_ERR(tlink)) return PTR_ERR(tlink); @@ -1915,7 +1924,8 @@ int cifs_unlink(struct inode *dir, struct dentry *dentry) cifs_drop_nlink(inode); } } else if (rc == -ENOENT) { - d_drop(dentry); + if (simple_positive(dentry)) + d_delete(dentry); } else if (rc == -EBUSY) { if (server->ops->rename_pending_delete) { rc = server->ops->rename_pending_delete(full_path, @@ -1968,6 +1978,8 @@ int cifs_unlink(struct inode *dir, struct dentry *dentry) kfree(attrs); free_xid(xid); cifs_put_tlink(tlink); + if (rehash) + d_rehash(dentry); return rc; }