From 3d69438031b00c601c991ab447cafb7d5c3c59a6 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Tue, 11 May 2010 14:59:55 -0400 Subject: [PATCH] cifs: guard against hardlinking directories When we made serverino the default, we trusted that the field sent by the server in the "uniqueid" field was actually unique. It turns out that it isn't reliably so. Samba, in particular, will just put the st_ino in the uniqueid field when unix extensions are enabled. When a share spans multiple filesystems, it's quite possible that there will be collisions. This is a server bug, but when the inodes in question are a directory (as is often the case) and there is a collision with the root inode of the mount, the result is a kernel panic on umount. Fix this by checking explicitly for directory inodes with the same uniqueid. If that is the case, then we can assume that using server inode numbers will be a problem and that they should be disabled. Fixes Samba bugzilla 7407 Signed-off-by: Jeff Layton CC: Stable Reviewed-and-Tested-by: Suresh Jayaraman Signed-off-by: Steve French --- fs/cifs/cifsglob.h | 1 + fs/cifs/inode.c | 21 +++++++++++++++++++-- 2 files changed, 20 insertions(+), 2 deletions(-) diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index ecf0ffbe2b64..0c2fd17439c8 100644 --- a/fs/cifs/cifsglob.h +++ b/fs/cifs/cifsglob.h @@ -502,6 +502,7 @@ struct dfs_info3_param { #define CIFS_FATTR_DFS_REFERRAL 0x1 #define CIFS_FATTR_DELETE_PENDING 0x2 #define CIFS_FATTR_NEED_REVAL 0x4 +#define CIFS_FATTR_INO_COLLISION 0x8 struct cifs_fattr { u32 cf_flags; diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c index 35ec11716213..29b9ea244c81 100644 --- a/fs/cifs/inode.c +++ b/fs/cifs/inode.c @@ -715,6 +715,16 @@ cifs_find_inode(struct inode *inode, void *opaque) if (CIFS_I(inode)->uniqueid != fattr->cf_uniqueid) return 0; + /* + * uh oh -- it's a directory. We can't use it since hardlinked dirs are + * verboten. Disable serverino and return it as if it were found, the + * caller can discard it, generate a uniqueid and retry the find + */ + if (S_ISDIR(inode->i_mode) && !list_empty(&inode->i_dentry)) { + fattr->cf_flags |= CIFS_FATTR_INO_COLLISION; + cifs_autodisable_serverino(CIFS_SB(inode->i_sb)); + } + return 1; } @@ -734,15 +744,22 @@ cifs_iget(struct super_block *sb, struct cifs_fattr *fattr) unsigned long hash; struct inode *inode; +retry_iget5_locked: cFYI(1, ("looking for uniqueid=%llu", fattr->cf_uniqueid)); /* hash down to 32-bits on 32-bit arch */ hash = cifs_uniqueid_to_ino_t(fattr->cf_uniqueid); inode = iget5_locked(sb, hash, cifs_find_inode, cifs_init_inode, fattr); - - /* we have fattrs in hand, update the inode */ if (inode) { + /* was there a problematic inode number collision? */ + if (fattr->cf_flags & CIFS_FATTR_INO_COLLISION) { + iput(inode); + fattr->cf_uniqueid = iunique(sb, ROOT_I); + fattr->cf_flags &= ~CIFS_FATTR_INO_COLLISION; + goto retry_iget5_locked; + } + cifs_fattr_to_inode(inode, fattr); if (sb->s_flags & MS_NOATIME) inode->i_flags |= S_NOATIME | S_NOCMTIME;