The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 2105c2820d366b76f38e6ad61c75771881ecc532 Mon Sep 17 00:00:00 2001
From: David Howells dhowells@redhat.com Date: Fri, 10 Apr 2020 15:23:27 +0100 Subject: [PATCH] afs: Fix race between post-modification dir edit and readdir/d_revalidate
AFS directories are retained locally as a structured file, with lookup being effected by a local search of the file contents. When a modification (such as mkdir) happens, the dir file content is modified locally rather than redownloading the directory.
The directory contents are accessed in a number of ways, with a number of different locks schemes:
(1) Download of contents - dvnode->validate_lock/write in afs_read_dir().
(2) Lookup and readdir - dvnode->validate_lock/read in afs_dir_iterate(), downgrading from (1) if necessary.
(3) d_revalidate of child dentry - dvnode->validate_lock/read in afs_do_lookup_one() downgrading from (1) if necessary.
(4) Edit of dir after modification - page locks on individual dir pages.
Unfortunately, because (4) uses different locking scheme to (1) - (3), nothing protects against the page being scanned whilst the edit is underway. Even download is not safe as it doesn't lock the pages - relying instead on the validate_lock to serialise as a whole (the theory being that directory contents are treated as a block and always downloaded as a block).
Fix this by write-locking dvnode->validate_lock around the edits. Care must be taken in the rename case as there may be two different dirs - but they need not be locked at the same time. In any case, once the lock is taken, the directory version must be rechecked, and the edit skipped if a later version has been downloaded by revalidation (there can't have been any local changes because the VFS holds the inode lock, but there can have been remote changes).
Fixes: 63a4681ff39c ("afs: Locally edit directory data for mkdir/create/unlink/...") Signed-off-by: David Howells dhowells@redhat.com
diff --git a/fs/afs/dir.c b/fs/afs/dir.c index 31d297e0f765..d6278616fb88 100644 --- a/fs/afs/dir.c +++ b/fs/afs/dir.c @@ -1275,6 +1275,7 @@ static int afs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) struct afs_fs_cursor fc; struct afs_vnode *dvnode = AFS_FS_I(dir); struct key *key; + afs_dataversion_t data_version; int ret;
mode |= S_IFDIR; @@ -1295,7 +1296,7 @@ static int afs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
ret = -ERESTARTSYS; if (afs_begin_vnode_operation(&fc, dvnode, key, true)) { - afs_dataversion_t data_version = dvnode->status.data_version + 1; + data_version = dvnode->status.data_version + 1;
while (afs_select_fileserver(&fc)) { fc.cb_break = afs_calc_vnode_cb_break(dvnode); @@ -1316,10 +1317,14 @@ static int afs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) goto error_key; }
- if (ret == 0 && - test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags)) - afs_edit_dir_add(dvnode, &dentry->d_name, &iget_data.fid, - afs_edit_dir_for_create); + if (ret == 0) { + down_write(&dvnode->validate_lock); + if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) && + dvnode->status.data_version == data_version) + afs_edit_dir_add(dvnode, &dentry->d_name, &iget_data.fid, + afs_edit_dir_for_create); + up_write(&dvnode->validate_lock); + }
key_put(key); kfree(scb); @@ -1360,6 +1365,7 @@ static int afs_rmdir(struct inode *dir, struct dentry *dentry) struct afs_fs_cursor fc; struct afs_vnode *dvnode = AFS_FS_I(dir), *vnode = NULL; struct key *key; + afs_dataversion_t data_version; int ret;
_enter("{%llx:%llu},{%pd}", @@ -1391,7 +1397,7 @@ static int afs_rmdir(struct inode *dir, struct dentry *dentry)
ret = -ERESTARTSYS; if (afs_begin_vnode_operation(&fc, dvnode, key, true)) { - afs_dataversion_t data_version = dvnode->status.data_version + 1; + data_version = dvnode->status.data_version + 1;
while (afs_select_fileserver(&fc)) { fc.cb_break = afs_calc_vnode_cb_break(dvnode); @@ -1404,9 +1410,12 @@ static int afs_rmdir(struct inode *dir, struct dentry *dentry) ret = afs_end_vnode_operation(&fc); if (ret == 0) { afs_dir_remove_subdir(dentry); - if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags)) + down_write(&dvnode->validate_lock); + if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) && + dvnode->status.data_version == data_version) afs_edit_dir_remove(dvnode, &dentry->d_name, afs_edit_dir_for_rmdir); + up_write(&dvnode->validate_lock); } }
@@ -1544,10 +1553,15 @@ static int afs_unlink(struct inode *dir, struct dentry *dentry) ret = afs_end_vnode_operation(&fc); if (ret == 0 && !(scb[1].have_status || scb[1].have_error)) ret = afs_dir_remove_link(dvnode, dentry, key); - if (ret == 0 && - test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags)) - afs_edit_dir_remove(dvnode, &dentry->d_name, - afs_edit_dir_for_unlink); + + if (ret == 0) { + down_write(&dvnode->validate_lock); + if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) && + dvnode->status.data_version == data_version) + afs_edit_dir_remove(dvnode, &dentry->d_name, + afs_edit_dir_for_unlink); + up_write(&dvnode->validate_lock); + } }
if (need_rehash && ret < 0 && ret != -ENOENT) @@ -1573,6 +1587,7 @@ static int afs_create(struct inode *dir, struct dentry *dentry, umode_t mode, struct afs_status_cb *scb; struct afs_vnode *dvnode = AFS_FS_I(dir); struct key *key; + afs_dataversion_t data_version; int ret;
mode |= S_IFREG; @@ -1597,7 +1612,7 @@ static int afs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
ret = -ERESTARTSYS; if (afs_begin_vnode_operation(&fc, dvnode, key, true)) { - afs_dataversion_t data_version = dvnode->status.data_version + 1; + data_version = dvnode->status.data_version + 1;
while (afs_select_fileserver(&fc)) { fc.cb_break = afs_calc_vnode_cb_break(dvnode); @@ -1618,9 +1633,12 @@ static int afs_create(struct inode *dir, struct dentry *dentry, umode_t mode, goto error_key; }
- if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags)) + down_write(&dvnode->validate_lock); + if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) && + dvnode->status.data_version == data_version) afs_edit_dir_add(dvnode, &dentry->d_name, &iget_data.fid, afs_edit_dir_for_create); + up_write(&dvnode->validate_lock);
kfree(scb); key_put(key); @@ -1648,6 +1666,7 @@ static int afs_link(struct dentry *from, struct inode *dir, struct afs_vnode *dvnode = AFS_FS_I(dir); struct afs_vnode *vnode = AFS_FS_I(d_inode(from)); struct key *key; + afs_dataversion_t data_version; int ret;
_enter("{%llx:%llu},{%llx:%llu},{%pd}", @@ -1672,7 +1691,7 @@ static int afs_link(struct dentry *from, struct inode *dir,
ret = -ERESTARTSYS; if (afs_begin_vnode_operation(&fc, dvnode, key, true)) { - afs_dataversion_t data_version = dvnode->status.data_version + 1; + data_version = dvnode->status.data_version + 1;
if (mutex_lock_interruptible_nested(&vnode->io_lock, 1) < 0) { afs_end_vnode_operation(&fc); @@ -1702,9 +1721,12 @@ static int afs_link(struct dentry *from, struct inode *dir, goto error_key; }
- if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags)) + down_write(&dvnode->validate_lock); + if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) && + dvnode->status.data_version == data_version) afs_edit_dir_add(dvnode, &dentry->d_name, &vnode->fid, afs_edit_dir_for_link); + up_write(&dvnode->validate_lock);
key_put(key); kfree(scb); @@ -1732,6 +1754,7 @@ static int afs_symlink(struct inode *dir, struct dentry *dentry, struct afs_status_cb *scb; struct afs_vnode *dvnode = AFS_FS_I(dir); struct key *key; + afs_dataversion_t data_version; int ret;
_enter("{%llx:%llu},{%pd},%s", @@ -1759,7 +1782,7 @@ static int afs_symlink(struct inode *dir, struct dentry *dentry,
ret = -ERESTARTSYS; if (afs_begin_vnode_operation(&fc, dvnode, key, true)) { - afs_dataversion_t data_version = dvnode->status.data_version + 1; + data_version = dvnode->status.data_version + 1;
while (afs_select_fileserver(&fc)) { fc.cb_break = afs_calc_vnode_cb_break(dvnode); @@ -1780,9 +1803,12 @@ static int afs_symlink(struct inode *dir, struct dentry *dentry, goto error_key; }
- if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags)) + down_write(&dvnode->validate_lock); + if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) && + dvnode->status.data_version == data_version) afs_edit_dir_add(dvnode, &dentry->d_name, &iget_data.fid, afs_edit_dir_for_symlink); + up_write(&dvnode->validate_lock);
key_put(key); kfree(scb); @@ -1812,6 +1838,8 @@ static int afs_rename(struct inode *old_dir, struct dentry *old_dentry, struct dentry *tmp = NULL, *rehash = NULL; struct inode *new_inode; struct key *key; + afs_dataversion_t orig_data_version; + afs_dataversion_t new_data_version; bool new_negative = d_is_negative(new_dentry); int ret;
@@ -1890,9 +1918,6 @@ static int afs_rename(struct inode *old_dir, struct dentry *old_dentry,
ret = -ERESTARTSYS; if (afs_begin_vnode_operation(&fc, orig_dvnode, key, true)) { - afs_dataversion_t orig_data_version; - afs_dataversion_t new_data_version; - orig_data_version = orig_dvnode->status.data_version + 1;
if (orig_dvnode != new_dvnode) { @@ -1928,18 +1953,25 @@ static int afs_rename(struct inode *old_dir, struct dentry *old_dentry, if (ret == 0) { if (rehash) d_rehash(rehash); - if (test_bit(AFS_VNODE_DIR_VALID, &orig_dvnode->flags)) - afs_edit_dir_remove(orig_dvnode, &old_dentry->d_name, - afs_edit_dir_for_rename_0); + down_write(&orig_dvnode->validate_lock); + if (test_bit(AFS_VNODE_DIR_VALID, &orig_dvnode->flags) && + orig_dvnode->status.data_version == orig_data_version) + afs_edit_dir_remove(orig_dvnode, &old_dentry->d_name, + afs_edit_dir_for_rename_0); + if (orig_dvnode != new_dvnode) { + up_write(&orig_dvnode->validate_lock);
- if (!new_negative && - test_bit(AFS_VNODE_DIR_VALID, &new_dvnode->flags)) - afs_edit_dir_remove(new_dvnode, &new_dentry->d_name, - afs_edit_dir_for_rename_1); + down_write(&new_dvnode->validate_lock); + } + if (test_bit(AFS_VNODE_DIR_VALID, &new_dvnode->flags) && + orig_dvnode->status.data_version == new_data_version) { + if (!new_negative) + afs_edit_dir_remove(new_dvnode, &new_dentry->d_name, + afs_edit_dir_for_rename_1);
- if (test_bit(AFS_VNODE_DIR_VALID, &new_dvnode->flags)) afs_edit_dir_add(new_dvnode, &new_dentry->d_name, &vnode->fid, afs_edit_dir_for_rename_2); + }
new_inode = d_inode(new_dentry); if (new_inode) { @@ -1958,6 +1990,7 @@ static int afs_rename(struct inode *old_dir, struct dentry *old_dentry, afs_update_dentry_version(&fc, old_dentry, &scb[1]); afs_update_dentry_version(&fc, new_dentry, &scb[1]); d_move(old_dentry, new_dentry); + up_write(&new_dvnode->validate_lock); goto error_tmp; }
diff --git a/fs/afs/dir_silly.c b/fs/afs/dir_silly.c index 361088a5edb9..d94e2b7cddff 100644 --- a/fs/afs/dir_silly.c +++ b/fs/afs/dir_silly.c @@ -21,6 +21,7 @@ static int afs_do_silly_rename(struct afs_vnode *dvnode, struct afs_vnode *vnode { struct afs_fs_cursor fc; struct afs_status_cb *scb; + afs_dataversion_t dir_data_version; int ret = -ERESTARTSYS;
_enter("%pd,%pd", old, new); @@ -31,7 +32,7 @@ static int afs_do_silly_rename(struct afs_vnode *dvnode, struct afs_vnode *vnode
trace_afs_silly_rename(vnode, false); if (afs_begin_vnode_operation(&fc, dvnode, key, true)) { - afs_dataversion_t dir_data_version = dvnode->status.data_version + 1; + dir_data_version = dvnode->status.data_version + 1;
while (afs_select_fileserver(&fc)) { fc.cb_break = afs_calc_vnode_cb_break(dvnode); @@ -54,12 +55,15 @@ static int afs_do_silly_rename(struct afs_vnode *dvnode, struct afs_vnode *vnode dvnode->silly_key = key_get(key); }
- if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags)) + down_write(&dvnode->validate_lock); + if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) && + dvnode->status.data_version == dir_data_version) { afs_edit_dir_remove(dvnode, &old->d_name, afs_edit_dir_for_silly_0); - if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags)) afs_edit_dir_add(dvnode, &new->d_name, &vnode->fid, afs_edit_dir_for_silly_1); + } + up_write(&dvnode->validate_lock); }
kfree(scb); @@ -181,10 +185,14 @@ static int afs_do_silly_unlink(struct afs_vnode *dvnode, struct afs_vnode *vnode clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags); } } - if (ret == 0 && - test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags)) - afs_edit_dir_remove(dvnode, &dentry->d_name, - afs_edit_dir_for_unlink); + if (ret == 0) { + down_write(&dvnode->validate_lock); + if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) && + dvnode->status.data_version == dir_data_version) + afs_edit_dir_remove(dvnode, &dentry->d_name, + afs_edit_dir_for_unlink); + up_write(&dvnode->validate_lock); + } }
kfree(scb);