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Message-Id: <20200422095052.581470468@linuxfoundation.org>
Date: Wed, 22 Apr 2020 11:56:02 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, David Howells <dhowells@...hat.com>
Subject: [PATCH 5.6 035/166] afs: Fix race between post-modification dir edit and readdir/d_revalidate
From: David Howells <dhowells@...hat.com>
commit 2105c2820d366b76f38e6ad61c75771881ecc532 upstream.
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@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
fs/afs/dir.c | 91 ++++++++++++++++++++++++++++++++++++-----------------
fs/afs/dir_silly.c | 22 ++++++++----
2 files changed, 77 insertions(+), 36 deletions(-)
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -1275,6 +1275,7 @@ static int afs_mkdir(struct inode *dir,
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,
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,
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 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,
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,
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,
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 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,
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,
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 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,
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,
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 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
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
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_
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_
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_
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);
-
- 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(&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);
+
+ 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_
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;
}
--- a/fs/afs/dir_silly.c
+++ b/fs/afs/dir_silly.c
@@ -21,6 +21,7 @@ static int afs_do_silly_rename(struct af
{
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 af
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 af
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 af
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);
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