Alyssa Ross <h...@alyssa.is> writes: > On Mon, May 12, 2025 at 07:51:53AM +0930, samiuddinsami.md...@gmail.com wrote: >> From: Sami Uddin <sami.md...@gmail.com> >> >> Prevent usage of shared memory regions where the length is zero, >> as such configurations are not valid and may lead to unexpected behavior. >> >> Signed-off-by: Sami Uddin <sami.md...@gmail.com> >> --- >> v3: >> - Use idiomatic 'if (!region->len)' as suggested by reviewer >> v2: >> - Fixed coding style issue: added space after 'if' statement >> >> include/linux/virtio_config.h | 2 ++ >> 1 file changed, 2 insertions(+) > > Hi, I'm sorry to be the bearer of bad news, but since this patch my VM > no longer works. The system is running wayland-proxy-virtwl[1] inside > a crosvm[2] VM, using crosvm's virtio-gpu device to do cross-domain > Wayland forwarding. > > Since this change, wayland-proxy-virtwl crashes with the following log > message: > > wl-proxy [WARNING]: Error handling client: Unix.Unix_error(Unix.EINVAL, > "DRM_IOCTL_VIRTGPU_RESOURCE_CREATE_BLOB", "") > > I'm pretty confused by what this change was supposed to do in the first > place… Looking at how virtio_get_shm_region() is used in > virtio_gpu_init(), it's called with a pointer to zeroed memory, and then > the get_shm_region() implementation is supposed to write to the region, > without ever reading from it as far as I can tell. Why is the initial > value of an out parameter being checked at all? How does this prevent > using zero-length shared memory regions? > > [1]: https://crosvm.dev/ > [2]: https://github.com/talex5/wayland-proxy-virtwl > > #regzbot introduced: 206cc44588f72b49ad4d7e21a7472ab2a72a83df
Okay, just found that it's already been reverted: https://lore.kernel.org/all/20250808072533-mutt-send-email-...@kernel.org/ Still, I'm confused how this was supposed to fix anything… #regzbot fix: Revert "virtio: reject shm region if length is zero"
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