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smb3: fix broken cached reads when posix locks

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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>
This commit is contained in:
Steve French 2024-08-15 18:31:36 -05:00
parent 47ac09b91b
commit e4be320eec
1 changed files with 1 additions and 3 deletions
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4
fs/smb/client/file.c
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@ -2912,9 +2912,7 @@ 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);