Re: Linux 2.6.38-rc6
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: 2011-02-25 00:55:40
Also in:
dri-devel, lkml
On Thu, Feb 24, 2011 at 4:48 PM, Anca Emanuel [off-list ref] wrote:
quoted hunk ↗ jump to hunk
diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c index e2bf953..e8f8925 100644 --- a/drivers/video/fbmem.c +++ b/drivers/video/fbmem.c@@ -1511,6 +1511,7 @@ void remove_conflicting_framebuffers(structapertures_struct *a, "%s vs %s - removing generic driver\n", name, registered_fb[i]->fix.id); unregister_framebuffer(registered_fb[i]); + registered_fb[i] = NULL; Tested the patch, and now I get this: dmesg: http://pastebin.com/ieMNrA7C [ 12.252328] BUG: unable to handle kernel NULL pointer dereference at 00000000000003b8 [ 12.252342] IP: [<ffffffff81311178>] fb_mmap+0x58/0x1d0
Ok, goodie.
Or not so goodie, but it does make it clear that yeah, the fb code
seems to be using stale pointers from that registered_fb[] array, and
the whole unregistration process is just racing with people using it.
Herton had that much bigger patch, can you test it?
Linus