Hi,
There are a number of potential NULL pointer dereferences in BTRFS - see
below.
Unfortunately I don't know what the best way to deal with these are in
BTRFS, so I'll leave the bug fixing to others and stick to just reporting
them.
In fs/btrfs/file.c::btrfs_file_aio_write() we do this:
...
pages = kmalloc(nrptrs * sizeof(struct page *), GFP_KERNEL);
...[skip lots of lines that don't touch 'pages']...
memset(pages, 0, sizeof(struct page *) * nrptrs);
ret = btrfs_delalloc_reserve_space(inode, write_bytes);
if (ret)
goto out;
ret = prepare_pages(root, file, pages, num_pages,
pos, first_index, last_index,
write_bytes);
...
since kmalloc() may fail and return a NULL pointer this could potentially
go bad.
Also in fs/btrfs/compression.c::btrfs_submit_compressed_write() there's
this:
...
cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
atomic_set(&cb->pending_bios, 0);
cb->errors = 0;
...
Which will also dereference a NULL pointer when kmalloc() fails.
and in the same function:
...
bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
bio->bi_private = cb;
...
bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
bio->bi_private = cb;
...
Which are also potential NULL derefs since (at least as far as I can
tell) compressed_bio_alloc() can also fail and return NULL.
And then in btrfs_submit_compressed_read() :
...
cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
atomic_set(&cb->pending_bios, 0);
cb->errors = 0;
...
cb->compressed_pages = kmalloc(sizeof(struct page *) * nr_pages,
GFP_NOFS);
bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
for (page_index = 0; page_index < nr_pages; page_index++) {
cb->compressed_pages[page_index] = alloc_page(GFP_NOFS |
__GFP_HIGHMEM);
}
...
comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
GFP_NOFS);
comp_bio->bi_private = cb;
...
All 3 risk dereferencing a NULL pointer when the allocations fail.
Enjoy ;-)
PS.
Please CC me on replies.
--
Jesper Juhl <jj@xxxxxxxxxxxxx> http://www.chaosbits.net/
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