• Maxim Patlasov's avatar
    fuse: fix fallocate vs. ftruncate race · 0ab08f57
    Maxim Patlasov authored
    
    
    A former patch introducing FUSE_I_SIZE_UNSTABLE flag provided detailed
    description of races between ftruncate and anyone who can extend i_size:
    
    > 1. As in the previous scenario fuse_dentry_revalidate() discovered that i_size
    > changed (due to our own fuse_do_setattr()) and is going to call
    > truncate_pagecache() for some  'new_size' it believes valid right now. But by
    > the time that particular truncate_pagecache() is called ...
    > 2. fuse_do_setattr() returns (either having called truncate_pagecache() or
    > not -- it doesn't matter).
    > 3. The file is extended either by write(2) or ftruncate(2) or fallocate(2).
    > 4. mmap-ed write makes a page in the extended region dirty.
    
    This patch adds necessary bits to fuse_file_fallocate() to protect from that
    race.
    Signed-off-by: default avatarMaxim Patlasov <mpatlasov@parallels.com>
    Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
    Cc: stable@vger.kernel.org
    0ab08f57
file.c 62.7 KB