linux-kernel - Kernel oops (bug) in fs/buffers.c:create_empty

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Date:	Sun, 6 Jul 2008 13:23:02 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	linux-kernel@...r.kernel.org, Al Viro <viro@...IV.linux.org.uk>
Cc:	akpm@...ux-foundation.org
Subject: Kernel oops (bug) in fs/buffers.c:create_empty_buffers

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?


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