From 698b368275c3fa98261159253cfc79653f9dffc6 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 11 May 2011 14:49:36 -0700 Subject: fbcon: add lifetime refcount to opened frame buffers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This just adds the refcount and the new registration lock logic. It does not (for example) actually change the read/write/ioctl routines to actually use the frame buffer that was opened: those function still end up alway susing whatever the current frame buffer is at the time of the call. Without this, if something holds the frame buffer open over a framebuffer switch, the close() operation after the switch will access a fb_info that has been free'd by the unregistering of the old frame buffer. (The read/write/ioctl operations will normally not cause problems, because they will - illogically - pick up the new fbcon instead. But a switch that happens just as one of those is going on might see problems too, the window is just much smaller: one individual op rather than the whole open-close sequence.) This use-after-free is apparently fairly easily triggered by the Ubuntu 11.04 boot sequence. Acked-by: Tim Gardner Tested-by: Daniel J Blueman Tested-by: Anca Emanuel Cc: Bruno Prémont Cc: Alan Cox Cc: Paul Mundt Cc: Dave Airlie Cc: Andy Whitcroft Signed-off-by: Linus Torvalds --- include/linux/fb.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/fb.h') diff --git a/include/linux/fb.h b/include/linux/fb.h index df728c1c29ed..6a8274877171 100644 --- a/include/linux/fb.h +++ b/include/linux/fb.h @@ -832,6 +832,7 @@ struct fb_tile_ops { #define FBINFO_CAN_FORCE_OUTPUT 0x200000 struct fb_info { + atomic_t count; int node; int flags; struct mutex lock; /* Lock for open/release/ioctl funcs */ -- cgit v1.2.3-59-g8ed1b