7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Lorenzo Stoakes (ARM) [ Upstream commit eae055f33e41e1d3e1a7e905bdcb1e9f196ed31d ] fb_deferred_io_init() allocates deferred I/O state, populating info->fbdefio_state, or leaving it NULL if an error occurs. Currently dlfb_ops_open() ignores its return value. Therefore if an error arises in fb_deferred_io_init() (for instance, due to an allocation failure) info->fbdefio_state is left NULL. fb_open() will then dereference a NULL pointer (calling fb_deferred_io_open()) as soon as dlfb_ops_open() returns. Additionally, if the allocation of info->fbdefio itself fails, dlfb_ops_open() sets info->fbdefio to NULL and invokes fb_deferred_io_init() regardless, hitting BUG_ON(!fbdefio). Fix this by only invoking fb_deferred_io_init() if the allocation succeeded, and checking for the error. The driver already supports operating without deferred I/O, so in either case fall back to that by setting info->fbdefio to NULL. The ignored return value was introduced in commit 56c134f7f1b5 ("fbdev: Track deferred-I/O pages in pageref struct"). However, the BUG_ON() issue originates from the earlier commit 5bea1fbf9423 ("staging: udlfb: fix incorrect fb_defio implementation for multiple framebuffers"), so target that for the fix. Fixes: 5bea1fbf9423 ("staging: udlfb: fix incorrect fb_defio implementation for multiple framebuffers") Cc: stable@vger.kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Helge Deller Signed-off-by: Sasha Levin --- drivers/video/fbdev/udlfb.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/video/fbdev/udlfb.c b/drivers/video/fbdev/udlfb.c index 92b352bc7e969..8b7b4bdac4fbf 100644 --- a/drivers/video/fbdev/udlfb.c +++ b/drivers/video/fbdev/udlfb.c @@ -947,10 +947,13 @@ static int dlfb_ops_open(struct fb_info *info, int user) fbdefio->delay = DL_DEFIO_WRITE_DELAY; fbdefio->sort_pagereflist = true; fbdefio->deferred_io = dlfb_dpy_deferred_io; - } - info->fbdefio = fbdefio; - fb_deferred_io_init(info); + info->fbdefio = fbdefio; + if (fb_deferred_io_init(info)) { + kfree(fbdefio); + info->fbdefio = NULL; + } + } } dev_dbg(info->dev, "open, user=%d fb_info=%p count=%d\n", -- 2.53.0