Christian Brauner <brauner@xxxxxxxxxx> writes: > On Tue, Apr 02, 2024 at 07:18:05PM -0700, Vinicius Costa Gomes wrote: >> Hi, >> >> Changes from RFC v3: >> - Removed the warning "fixes" patches, as they could hide potencial >> bugs (Christian Brauner); >> - Added "cred-specific" macros (Christian Brauner), from my side, >> added a few '_' to the guards to signify that the newly introduced >> helper macros are preferred. >> - Changed a few guard() to scoped_guard() to fix the clang (17.0.6) >> compilation error about 'goto' bypassing variable initialization; >> >> Link to RFC v3: >> >> https://lore.kernel.org/r/20240216051640.197378-1-vinicius.gomes@xxxxxxxxx/ >> >> Changes from RFC v2: >> - Added separate patches for the warnings for the discarded const >> when using the cleanup macros: one for DEFINE_GUARD() and one for >> DEFINE_LOCK_GUARD_1() (I am uncertain if it's better to squash them >> together); >> - Reordered the series so the backing file patch is the first user of >> the introduced helpers (Amir Goldstein); >> - Change the definition of the cleanup "class" from a GUARD to a >> LOCK_GUARD_1, which defines an implicit container, that allows us >> to remove some variable declarations to store the overriden >> credentials (Amir Goldstein); >> - Replaced most of the uses of scoped_guard() with guard(), to reduce >> the code churn, the remaining ones I wasn't sure if I was changing >> the behavior: either they were nested (overrides "inside" >> overrides) or something calls current_cred() (Amir Goldstein). >> >> New questions: >> - The backing file callbacks are now called with the "light" >> overriden credentials, so they are kind of restricted in what they >> can do with their credentials, is this acceptable in general? > > Until we grow additional users, I think yes. Just needs to be > documented. > Will add some documentation for it, then. >> - in ovl_rename() I had to manually call the "light" the overrides, >> both using the guard() macro or using the non-light version causes >> the workload to crash the kernel. I still have to investigate why >> this is happening. Hints are appreciated. > > Do you have a reproducer? Do you have a splat from dmesg? Just to be sure, with this version of the series the crash doesn't happen. It was only happening when I was using the guard() macro everywhere. I just looked at my crash collection and couldn't find the splats, from what I remember I lost connection to the machine, and wasn't able to retrieve the splat. I believe the crash and clang 17 compilation error point to the same problem, that in ovl_rename() some 'goto' skips the declaration of the (implicit) variable that the guard() macro generates. And it ends up doing a revert_creds_light() on garbage memory when ovl_rename() returns. (if you want I can try and go back to "guard() everywhere" and try a bit harder to get a splat) Does that make sense? Cheers, -- Vinicius
