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cifs: Fix race between hole punch and page fault 

Cifs has a following race between hole punching and page fault:

CPU1                                            CPU2
smb3_fallocate()
  smb3_punch_hole()
    truncate_pagecache_range()
                                                filemap_fault()
                                                  - loads old data into the
                                                    page cache
    SMB2_ioctl(..., FSCTL_SET_ZERO_DATA, ...)

And now we have stale data in the page cache. Fix the problem by locking
out faults (as well as reads) using mapping->invalidate_lock while hole
punch is running.

CC: Steve French <sfrench@samba.org>
CC: linux-cifs@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Jan Kara 2021-04-22 16:52:32 +02:00
parent 057ba5b245
commit b092b3efc7
1 changed files with 2 additions and 0 deletions
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2
fs/cifs/smb2ops.c
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@ -3588,6 +3588,7 @@ static long smb3_punch_hole(struct file *file, struct cifs_tcon *tcon,
return rc;
}
filemap_invalidate_lock(inode->i_mapping);
/*
* We implement the punch hole through ioctl, so we need remove the page
* caches first, otherwise the data may be inconsistent with the server.
@ -3605,6 +3606,7 @@ static long smb3_punch_hole(struct file *file, struct cifs_tcon *tcon,
sizeof(struct file_zero_data_information),
CIFSMaxBufSize, NULL, NULL);
free_xid(xid);
filemap_invalidate_unlock(inode->i_mapping);
return rc;
}