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alistair23-linux/fs/afs
David Howells 00d3928737 afs: Fix race between post-modification dir edit and readdir/d_revalidate
commit 2105c2820d 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: 63a4681ff3 ("afs: Locally edit directory data for mkdir/create/unlink/...")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-04-23 10:36:25 +02:00
..
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Makefile afs: do not send list of client addresses 2019-06-02 18:06:26 -07:00
addr_list.c Keyrings namespacing 2019-07-08 19:36:47 -07:00
afs.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
afs_cm.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
afs_fs.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
afs_vl.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
cache.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
callback.c afs: Fix possible assert with callbacks from yfs servers 2019-11-22 14:19:26 -08:00
cell.c afs: Fix characters allowed into cell names 2020-01-29 16:45:24 +01:00
cmservice.c afs: Fix handling of an abort from a service handler 2020-04-01 11:02:04 +02:00
dir.c afs: Fix race between post-modification dir edit and readdir/d_revalidate 2020-04-23 10:36:25 +02:00
dir_edit.c afs: Remove set but not used variables 'before', 'after' 2020-01-26 10:01:08 +01:00
dir_silly.c afs: Fix race between post-modification dir edit and readdir/d_revalidate 2020-04-23 10:36:25 +02:00
dynroot.c afs: Fix creation calls in the dynamic root to fail with EOPNOTSUPP 2020-01-09 10:19:48 +01:00
file.c fs: afs: Fix a possible null-pointer dereference in afs_put_read() 2019-07-30 14:38:51 +01:00
flock.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
fs_probe.c afs: Fix unpinned address list during probing 2020-04-01 11:02:08 +02:00
fsclient.c afs: Fix rename operation status delivery 2020-04-23 10:36:25 +02:00
inode.c afs dynroot: switch to simple_dir_operations 2019-09-15 12:19:48 -04:00
internal.h afs: Fix handling of an abort from a service handler 2020-04-01 11:02:04 +02:00
main.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
misc.c AFS development 2019-07-10 20:55:33 -07:00
mntpt.c afs: Fix mountpoint parsing 2020-01-09 10:19:48 +01:00
proc.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
protocol_uae.h afs: Add support for the UAE error table 2019-06-28 18:37:53 +01:00
protocol_yfs.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
rotate.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
rxrpc.c rxrpc: Fix call interruptibility handling 2020-04-17 10:49:57 +02:00
security.c afs: Support RCU pathwalk 2019-09-02 11:43:54 +01:00
server.c afs: Fix afs_find_server lookups for ipv4 peers 2020-01-09 10:19:43 +01:00
server_list.c AFS development 2019-07-10 20:55:33 -07:00
super.c afs: Fix missing cell comparison in afs_test_super() 2020-01-17 19:48:29 +01:00
vl_list.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
vl_probe.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
vl_rotate.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
vlclient.c afs: Fix loop index mixup in afs_deliver_vl_get_entry_by_name_u() 2019-07-30 14:38:51 +01:00
volume.c afs: remove unused variable 'afs_voltypes' 2019-09-02 11:43:54 +01:00
write.c AFS development 2019-07-10 20:55:33 -07:00
xattr.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
xdr_fs.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
yfsclient.c afs: Fix rename operation status delivery 2020-04-23 10:36:25 +02:00