Messages in this thread | | | Date | Thu, 10 Jul 2008 00:46:37 +0200 | From | Jan Kara <> | Subject | Re: Kernel oops (bug) in fs/buffers.c:create_empty_buffers |
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> On Sun, 6 Jul 2008 13:23:02 -0700 Arjan van de Ven <arjan@infradead.org> wrote: > > Hi, > > > > caught this one on kerneloops.org: > > http://www.kerneloops.org/searchweek.php?search=create_empty_buffers > > > > void create_empty_buffers(struct page *page, > > unsigned long blocksize, unsigned long b_state) > > { > > struct buffer_head *bh, *head, *tail; > > > > head = alloc_page_buffers(page, blocksize, 1); > > bh = head; > > do { > > bh->b_state |= b_state; > > tail = bh; > > bh = bh->b_this_page; > > } while (bh); > > > > > > turns out, alloc_page_buffers() can fail and return NULL (for AIO for > > example)... yet this code blindly dereferences the result, getting a > > predictable NULL pointer fault. > > > > It's not directly clear what to do about... make this function return > > the failure to the caller? > > isofs has a habit of returning impossible block sizes and the > > while ((offset -= size) >= 0) { > > consequently loops zero times and alloc_page_buffers() returns null. > > Someone was having a look at it - maybe Jan? Yes, I was looking at that. Actually, I've pinpointed the cause of the Oopses I've seen to a bug in ide-cd driver. It happily sets blocksize to whatever value the drive reported and some drives have a habit of reporting bogus values when unreadable medium is inserted. Jens has actually cooked up a fix for this bug (http://thread.gmane.org/gmane.linux.kernel/696582) and it fixes the problem at least for me.
> I assume that the kernloops.org records link back to the original > report somewhere but I can't find it?
Honza -- Jan Kara <jack@suse.cz> SuSE CR Labs
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