On Wed, 2026-09-02 at 18:00 +0530, Sajal Gupta wrote:
> The plane property loop uses req->properties[num_properties + i] as write
> index while simultaneously incrementing `num_properties` inside the loop.
> At iteration i, num_properties has also incremented by i, so the write
> is done at `initial_num_properties + 2*i`, skipping every other index and
> advancing by 2 per iteration.
>
> With just 2 connector and 32 plane properties the last write happens at
> index 64, one slot past the end of the 64-slot (indices 0–63)
> allocation. A USB device can trigger OOB by advertising the maximum
> number of properties.
>
> Fix by dropping the redundant `+ i`; num_properties is already the correct
> running index, as gud_connector_fill_properties() fills the preceding
> slots.
>
> Fixes: 40e1a70b4aed ("drm: Add GUD USB Display driver")
> Reported-by: Sashiko <[email protected]>
> Link:
> https://sashiko.dev/#/patchset/20260821071812.16500-1-sajal2005gupta%40gmail.com?part=1
> Signed-off-by: Sajal Gupta <[email protected]>
Cc: <[email protected]>
Acked-by: Ruben Wauters <[email protected]>Sorry, for some reason I didn't receive this patch in my mailbox, only by manually searching for patches did I find it, thanks for the patch. > --- > > Verified with KASAN using a raw-gadget fake GUD device reporting 2 > connector properties and 32 plane properties: > > BUG: KASAN: slab-out-of-bounds in gud_plane_atomic_check+0x1352/0x1ba0 > Write of size 2 at addr ffff88800d029a9a by task temm/270 > > Call Trace: > <TASK> > kasan_report+0xfa/0x120 > gud_plane_atomic_check+0x1352/0x1ba0 > drm_atomic_helper_check_planes+0x2f2/0x9b0 > drm_atomic_helper_check+0x72/0x140 > drm_atomic_check_only+0x127b/0x3420 > drm_atomic_commit+0x124/0x2e0 > drm_atomic_helper_set_config+0xd9/0x130 > drm_mode_setcrtc+0xcfd/0x1b20 > drm_ioctl_kernel+0x167/0x2d0 > drm_ioctl+0x53f/0xbe0 > __x64_sys_ioctl+0x137/0x1c0 > do_syscall_64+0xde/0x4b0 > </TASK> > > The buggy address is located 0 bytes to the right of > allocated 666-byte region [ffff88800d029800, ffff88800d029a9a) > > > drivers/gpu/drm/gud/gud_pipe.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c > index 5ef887d8485a..54adc401bc1b 100644 > --- a/drivers/gpu/drm/gud/gud_pipe.c > +++ b/drivers/gpu/drm/gud/gud_pipe.c > @@ -562,8 +562,8 @@ int gud_plane_atomic_check(struct drm_plane *plane, > goto out; > } > > - req->properties[num_properties + i].prop = cpu_to_le16(prop); > - req->properties[num_properties + i].val = cpu_to_le64(val); > + req->properties[num_properties].prop = cpu_to_le16(prop); > + req->properties[num_properties].val = cpu_to_le64(val); > num_properties++; > } > > -- > 2.55.0
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