On Mon, 22 Sep 2014, Anton Altaparmakov wrote: > Any code that uses __getblk() and thus bread(), breadahead(), sb_bread(), > sb_breadahead(), sb_getblk(), and calls it using a 64-bit block on a > 32-bit arch (where "long" is 32-bit) causes an inifinite loop in > __getblk_slow() with an infinite stream of errors logged to dmesg like > this: > > __find_get_block_slow() failed. block=6740375944, b_blocknr=2445408648 > b_state=0x00000020, b_size=512 > device sda1 blocksize: 512 > > Note how in hex block is 0x191C1F988 and b_blocknr is 0x91C1F988 i.e. the > top 32-bits are missing (in this case the 0x1 at the top). > > This is because grow_dev_page() was broken in commit 676ce6d5ca30: "block: > replace __getblk_slow misfix by grow_dev_page fix" by Hugh Dickins so that > it now has a 32-bit overflow due to shifting the block value to the right > so it fits in 32-bits and storing the result in pgoff_t variable which is > 32-bit and then passing the pgoff_t variable left-shifted as the block > number which causes the top bits to get lost as the pgoff_t is not type > cast to sector_t / 64-bit before the shift. > > This patch fixes this issue by type casting "index" to sector_t before > doing the left shift. > > Note this is not a theoretical bug but has been seen in the field on a > 4TiB hard drive with logical sector size 512 bytes. > > This patch has been verified to fix the infinite loop problem on 3.17-rc5 > kernel using a 4TB disk image mounted using "-o loop". Without this patch > doing a "find /nt" where /nt is an NTFS volume causes the inifinite loop > 100% reproducibly whilst with the patch it works fine as expected. > > Signed-off-by: Anton Altaparmakov <aia21@xxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx # 3.6 3.8 3.10 3.12 3.14 3.16 Acked-by: Hugh Dickins <hughd@xxxxxxxxxx> Yes indeed, that's bad, and entirely my fault (though it took me a while to see how the "block = index << sizebits" which was there before was okay, but my passing "index << sizebits" as arg to function very much not okay). Thank you, Anton. But I see my commit was marked for stable 3.0 3.2 3.4 3.5: so your fix is needed in 3.2 and 3.4 longterm also (the others now beyond life). Hugh > --- > > Linus, can you please apply this? Alternatively, Andrew, can you please > pick this up and send it to Linus? > > It would be good it it can be applied for 3.17 as well as to all stable > kernels >= 3.6 as they are all broken! > > Thanks a lot in advance! > > Best regards, > > Anton > -- > Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @) > Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK > Linux NTFS maintainer, http://www.linux-ntfs.org/ > > diff --git a/fs/buffer.c b/fs/buffer.c > index 8f05111..3588a80 100644 > --- a/fs/buffer.c > +++ b/fs/buffer.c > @@ -1022,7 +1022,8 @@ grow_dev_page(struct block_device *bdev, sector_t block, > bh = page_buffers(page); > if (bh->b_size == size) { > end_block = init_page_buffers(page, bdev, > - index << sizebits, size); > + (sector_t)index << sizebits, > + size); > goto done; > } > if (!try_to_free_buffers(page)) > @@ -1043,7 +1044,8 @@ grow_dev_page(struct block_device *bdev, sector_t block, > */ > spin_lock(&inode->i_mapping->private_lock); > link_dev_buffers(page, bh); > - end_block = init_page_buffers(page, bdev, index << sizebits, size); > + end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits, > + size); > spin_unlock(&inode->i_mapping->private_lock); > done: > ret = (block < end_block) ? 1 : -ENXIO; -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
