On Thu, Mar 07, 2024 at 10:08:13AM -0500, Sweet Tea Dorminy wrote: > All calls into generic vfs functions need to make sure that the inode > attributes used by those functions are up to date, by calling > fuse_update_attributes() as appropriate. > > generic_write_checks() accesses inode size in order to get the > appropriate file offset for files opened with O_APPEND. Currently, in > some cases, fuse_update_attributes() is not called before > generic_write_checks(), potentially resulting in corruption/overwrite of > previously appended data if i_size is out of date in the cached inode. > > Therefore, make sure fuse_update_attributes() is always > called before generic_write_checks(), and add a note about why it's not > necessary for some llseek calls. > > Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@xxxxxxxxxx> I had to ask questions and go look at the code, mostly because I'm not a FUSE developer. fuse_update_attributes() doesn't actually do anything if the stats aren't invalidated, I was concerned we were suddenly adding a lot of overhead for every write call. Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx> I have a question for the normal FUSE developers, how would one test this? There doesn't appear to be a mechanism for writing stub FUSE fs's to exercise a case like this in fstests. Is there some other way you guys would test this or is this something we need to build out ourselves? Thanks, Josef
