From 836bb3268db405cf9021496ac4dbc26d3e4758fe Mon Sep 17 00:00:00 2001 From: Steve French Date: Thu, 15 Aug 2024 14:03:43 -0500 Subject: [PATCH] smb3: fix lock breakage for cached writes Mandatory locking is enforced for cached writes, which violates default posix semantics, and also it is enforced inconsistently. This apparently breaks recent versions of libreoffice, but can also be demonstrated by opening a file twice from the same client, locking it from handle one and writing to it from handle two (which fails, returning EACCES). Since there was already a mount option "forcemandatorylock" (which defaults to off), with this change only when the user intentionally specifies "forcemandatorylock" on mount will we break posix semantics on write to a locked range (ie we will only fail the write in this case, if the user mounts with "forcemandatorylock"). Fixes: 85160e03a79e ("CIFS: Implement caching mechanism for mandatory brlocks") Cc: stable@vger.kernel.org Cc: Pavel Shilovsky Reported-by: abartlet@samba.org Reported-by: Kevin Ottens Reviewed-by: David Howells Signed-off-by: Steve French --- fs/smb/client/file.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c index 45459af5044d..06a0667f8ff2 100644 --- a/fs/smb/client/file.c +++ b/fs/smb/client/file.c @@ -2753,6 +2753,7 @@ cifs_writev(struct kiocb *iocb, struct iov_iter *from) struct inode *inode = file->f_mapping->host; struct cifsInodeInfo *cinode = CIFS_I(inode); struct TCP_Server_Info *server = tlink_tcon(cfile->tlink)->ses->server; + struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb); ssize_t rc; rc = netfs_start_io_write(inode); @@ -2769,12 +2770,16 @@ cifs_writev(struct kiocb *iocb, struct iov_iter *from) if (rc <= 0) goto out; - if (!cifs_find_lock_conflict(cfile, iocb->ki_pos, iov_iter_count(from), + if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) && + (cifs_find_lock_conflict(cfile, iocb->ki_pos, iov_iter_count(from), server->vals->exclusive_lock_type, 0, - NULL, CIFS_WRITE_OP)) - rc = netfs_buffered_write_iter_locked(iocb, from, NULL); - else + NULL, CIFS_WRITE_OP))) { rc = -EACCES; + goto out; + } + + rc = netfs_buffered_write_iter_locked(iocb, from, NULL); + out: up_read(&cinode->lock_sem); netfs_end_io_write(inode);