On Wed, Oct 23, 2024 at 01:23:14PM -0400, Taylor Blau wrote: > On Wed, Oct 23, 2024 at 05:04:58PM +0200, Patrick Steinhardt wrote: > > Unless told otherwise, Windows will keep other processes from reading, > > writing and deleting files when one has an open handle that was created > > via `CreateFileW()`. This behaviour can be altered via `FILE_SHARE_*` > > flags such that other processes _can_ read and/or modify such a file. > > This sharing mechanism is quite important in the context of Git, as we > > assume POSIX semantics all over the place. > > > > There are two calls where we don't set up those flags though: > > > > - We don't set `FILE_SHARE_DELETE` when creating a file for appending > > via `mingw_open_append()`. This makes it impossible to delete the > > file from another process or to replace it via an atomic rename. > > > > - When opening a file such that we can change its access/modification > > times. This makes it impossible to perform any kind of operation > > on this file at all from another process. While we only open the > > file for a short amount of time to update its timestamps, this still > > opens us up for a race condition with another process. > > > > Adapt both of these callsites to pass all three sharing flags. > > Interesting, and especially so noting that we *do* call CreateFileW() > with the FILE_SHARE_DELETE flag in other functions like create_watch(), > mingw_open_existing(), mingw_getcwd(), etc. Heh. mingw_open_existing() passes FILE_SHARE_DELETE because you added it. Can you tell which branch I'm 'git grep'-ing on? ;-) Thanks, Taylor
