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TAGGED_RCPT(0.00)[2442951a6abb004df963]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,suse.de:dkim,suse.com:url,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,appspotmail.com:email] X-Spam-Flag: NO X-Spam-Score: -3.01 X-Spam-Level: X-Rspamd-Queue-Id: 1239E1F7F6 X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action Merged into drm-misc-fixes Am 25.08.26 um 14:07 schrieb Slawomir Stepien: > The `cirrus-qemu` driver relies on `CIRRUS_VRAM_SIZE` (4 MB) to validate > framebuffer sizes. However, during PCI probe, the driver mapped BAR0 > without verifying that its size matches `CIRRUS_VRAM_SIZE`. > > If a PCI device with a BAR0 smaller than 4 MB is bound to the driver, the > mapped VRAM will be smaller than expected. Because validation checks assume > 4 MB VRAM, framebuffers larger than the mapped memory can be created. > > When the display plane is updated (e.g. during release), > `cirrus_primary_plane_helper_atomic_update()` copies the framebuffer to > VRAM using `drm_fb_memcpy()`. Writing past the end of the mapped I/O memory > causes a supervisor write page fault: > > BUG: unable to handle page fault for address: ffffc9000389c000 > ... > RIP: 0010:memcpy_toio+0x7c/0xe0 arch/x86/lib/iomem.c:110 > ... > Call Trace: > > iosys_map_memcpy_to include/linux/iosys-map.h:285 [inline] > drm_fb_memcpy+0x325/0x5d0 drivers/gpu/drm/drm_format_helper.c:442 > cirrus_primary_plane_helper_atomic_update+0x98a/0xb00 > drivers/gpu/drm/tiny/cirrus-qemu.c:358 > drm_atomic_helper_commit_planes+0x626/0xea0 > drivers/gpu/drm/drm_atomic_helper.c:3038 > drm_atomic_helper_commit_tail+0x60/0x510 > drivers/gpu/drm/drm_atomic_helper.c:1989 > commit_tail+0x2b1/0x3c0 drivers/gpu/drm/drm_atomic_helper.c:2074 > drm_atomic_helper_commit+0xa77/0xb10 > drivers/gpu/drm/drm_atomic_helper.c:2312 > > Fix this by validating in `cirrus_pci_probe()` that the PCI BAR0 resource > is not less than `CIRRUS_VRAM_SIZE`, returning `-ENODEV` if it is less. > > Fixes: ab3e023b1b4c ("drm/cirrus: rewrite and modernize driver.") > Assisted-by: Gemini:gemini-3.6-flash Gemini:gemini-3.1-pro-preview syzbot > Reported-by: syzbot+2442951a6abb004df963@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=2442951a6abb004df963 > Link: https://syzkaller.appspot.com/ai_job?id=ba262a3a-bccf-4ad8-a1b0-583c55d34fd6 > Signed-off-by: Slawomir Stepien > --- > v2: > * move the check before aperture_remove_conflicting_pci_devices() as suggested by sashiko. > * check if the pci_resource_len() for BAR0 is less than CIRRUS_VRAM_SIZE as suggested by Thomas. The > qemu emulates 4, (8 and 16 MB for compatibility) - never less than 4MB. > > v1: > * https://lore.kernel.org/all/b11f8965-5896-4119-98b7-6bd0eb9fa139@mail.kernel.org/T/ > --- > drivers/gpu/drm/tiny/cirrus-qemu.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/gpu/drm/tiny/cirrus-qemu.c b/drivers/gpu/drm/tiny/cirrus-qemu.c > index 075221b431d3..3bf23fcf6574 100644 > --- a/drivers/gpu/drm/tiny/cirrus-qemu.c > +++ b/drivers/gpu/drm/tiny/cirrus-qemu.c > @@ -582,6 +582,9 @@ static int cirrus_pci_probe(struct pci_dev *pdev, > struct cirrus_device *cirrus; > int ret; > > + if (pci_resource_len(pdev, 0) < CIRRUS_VRAM_SIZE) > + return -ENODEV; > + > ret = aperture_remove_conflicting_pci_devices(pdev, cirrus_driver.name); > if (ret) > return ret; -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com GF: Jochen Jaser, Andrew McDonald, (HRB 36809, AG Nürnberg)