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smb3: fix broken cached reads when posix locks

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commit e4be320eec upstream.

Mandatory locking is enforced for cached reads, which violates
default posix semantics, and also it is enforced inconsistently.
This affected recent versions of libreoffice, and can be
demonstrated by opening a file twice from the same client,
locking it from handle one and trying to read from it from
handle two (which fails, returning EACCES).

There is already a mount option "forcemandatorylock"
(which defaults to off), so with this change only when the user
intentionally specifies "forcemandatorylock" on mount will we
break posix semantics on read to a locked range (ie we will
only fail in this case, if the user mounts with
"forcemandatorylock").

An earlier patch fixed the write path.

Fixes: 85160e03a7 ("CIFS: Implement caching mechanism for mandatory brlocks")
Cc: stable@vger.kernel.org
Cc: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: David Howells <dhowells@redhat.com>
Reported-by: abartlet@samba.org
Reported-by: Kevin Ottens <kevin.ottens@enioka.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Steve French
2024-08-15 18:31:36 -05:00
committed by Greg Kroah-Hartman
parent 8952352329
commit 5364577629
1 changed files with 1 additions and 3 deletions
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fs/smb/client/file.c
+1 -3
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@@ -2911,9 +2911,7 @@ cifs_strict_readv(struct kiocb *iocb, struct iov_iter *to)
if (!CIFS_CACHE_READ(cinode))
return netfs_unbuffered_read_iter(iocb, to);
if (cap_unix(tcon->ses) &&
(CIFS_UNIX_FCNTL_CAP & le64_to_cpu(tcon->fsUnixInfo.Capability)) &&
((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0)) {
if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0) {
if (iocb->ki_flags & IOCB_DIRECT)
return netfs_unbuffered_read_iter(iocb, to);
return netfs_buffered_read_iter(iocb, to);