Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
drm/ssd130x: Fix an oops when attempting to update a disabled plane
Geert reports that the following NULL pointer dereference happens for him after commit 49d7d58 ("drm/ssd130x: Don't allocate buffers on each plane update"): [drm] Initialized ssd130x 1.0.0 20220131 for 0-003c on minor 0 ssd130x-i2c 0-003c: [drm] surface width(128), height(32), bpp(1) and format(R1 little-endian (0x20203152)) Unable to handle kernel NULL pointer dereference at virtual address 00000000 Oops [#1] CPU: 0 PID: 1 Comm: swapper Not tainted 6.5.0-rc1-orangecrab-02219-g0a529a1e4bf4 torvalds#565 epc : ssd130x_update_rect.isra.0+0x13c/0x340 ra : ssd130x_update_rect.isra.0+0x2bc/0x340 ... status: 00000120 badaddr: 00000000 cause: 0000000f [<c0303d90>] ssd130x_update_rect.isra.0+0x13c/0x340 [<c0304200>] ssd130x_primary_plane_helper_atomic_update+0x26c/0x284 [<c02f8d54>] drm_atomic_helper_commit_planes+0xfc/0x27c [<c02f9314>] drm_atomic_helper_commit_tail+0x5c/0xb4 [<c02f94fc>] commit_tail+0x190/0x1b8 [<c02f99fc>] drm_atomic_helper_commit+0x194/0x1c0 [<c02c5d00>] drm_atomic_commit+0xa4/0xe4 [<c02cce40>] drm_client_modeset_commit_atomic+0x244/0x278 [<c02ccef0>] drm_client_modeset_commit_locked+0x7c/0x1bc [<c02cd064>] drm_client_modeset_commit+0x34/0x64 [<c0301a78>] __drm_fb_helper_restore_fbdev_mode_unlocked+0xc4/0xe8 [<c0303424>] drm_fb_helper_set_par+0x38/0x58 [<c027c410>] fbcon_init+0x294/0x534 ... The problem is that fbcon calls fbcon_init() which triggers a DRM modeset and this leads to drm_atomic_helper_commit_planes() attempting to commit the atomic state for all planes, even the ones whose CRTC is not enabled. Since the primary plane buffer is allocated in the encoder .atomic_enable callback, this happens after that initial modeset commit and leads to the mentioned NULL pointer dereference. Fix this by allocating the buffers in the struct drm_plane_helper_funcs .begin_fb_access callback and free them in to .end_fb_access callback, instead of doing it when the encoder is enabled. Fixes: 49d7d58 ("drm/ssd130x: Don't allocate buffers on each plane update") Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
- Loading branch information