Message ID | 4FBFE0F9.8050509@redhat.com |
---|---|
State | Accepted, archived |
Headers | show |
On 2012-05-25, at 1:43 PM, Eric Sandeen wrote: > In short, for a completely full filesystem with more than 2^32 > blocks, the rbtree bitmap backend can assemble an extent of used > blocks which is longer than 2^32. If it does, it will overflow > ->count, and corrupt the rbtree for the bitmaps. > > Discovered by completely filling a 32T filesystem using fallocate, and > then observing debugfs, dumpe2fs, and e2fsck all behaving badly. > > (Note that filling with only 31 x 1T files did not show the problem, > because freespace was fragmented enough that there was no sufficiently > long range of used blocks.) > > Signed-off-by: Eric Sandeen <sandeen@redhat.com> > --- > > An alternative solution might be to limit the rb_extent to > 32-bit counts, and not merging beyond that. For fragmented > freespace, as normal, perhaps that would be a better memory > savings? But this fixes the immediate problem and seems worth > merging to avoid bad situations such as e2fsck corrupting a > perfectly good 32T filesystem... That was my initial thought as well, but the bmap_rb_extent struct already has several 64-bit values in it on a 64-bit arch, so there would not be any space savings. On a 32-bit arch, in theory we could save 8 bytes by locating a 32-bit count adjacent to rb_node instead of after __u64 start, but then 32-bit systems can't handle block devices over 16TB anyway, so the point is moot... Reviewed-by: Andreas Dilger <adilger@whamcloud.com> > diff --git a/lib/ext2fs/blkmap64_rb.c b/lib/ext2fs/blkmap64_rb.c > index 7ab72f4..a83f8ac 100644 > --- a/lib/ext2fs/blkmap64_rb.c > +++ b/lib/ext2fs/blkmap64_rb.c > @@ -33,7 +33,7 @@ > struct bmap_rb_extent { > struct rb_node node; > __u64 start; > - __u32 count; > + __u64 count; > }; > > struct ext2fs_rb_private { > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html Cheers, Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, May 25, 2012 at 02:43:53PM -0500, Eric Sandeen wrote: > Well, this took way too long to find, in retrospect. > > In short, for a completely full filesystem with more than 2^32 > blocks, the rbtree bitmap backend can assemble an extent of used > blocks which is longer than 2^32. If it does, it will overflow > ->count, and corrupt the rbtree for the bitmaps. > > Discovered by completely filling a 32T filesystem using fallocate, and > then observing debugfs, dumpe2fs, and e2fsck all behaving badly. > > (Note that filling with only 31 x 1T files did not show the problem, > because freespace was fragmented enough that there was no sufficiently > long range of used blocks.) > > Signed-off-by: Eric Sandeen <sandeen@redhat.com> Thanks, applied. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/lib/ext2fs/blkmap64_rb.c b/lib/ext2fs/blkmap64_rb.c index 7ab72f4..a83f8ac 100644 --- a/lib/ext2fs/blkmap64_rb.c +++ b/lib/ext2fs/blkmap64_rb.c @@ -33,7 +33,7 @@ struct bmap_rb_extent { struct rb_node node; __u64 start; - __u32 count; + __u64 count; }; struct ext2fs_rb_private {
Well, this took way too long to find, in retrospect. In short, for a completely full filesystem with more than 2^32 blocks, the rbtree bitmap backend can assemble an extent of used blocks which is longer than 2^32. If it does, it will overflow ->count, and corrupt the rbtree for the bitmaps. Discovered by completely filling a 32T filesystem using fallocate, and then observing debugfs, dumpe2fs, and e2fsck all behaving badly. (Note that filling with only 31 x 1T files did not show the problem, because freespace was fragmented enough that there was no sufficiently long range of used blocks.) Signed-off-by: Eric Sandeen <sandeen@redhat.com> --- An alternative solution might be to limit the rb_extent to 32-bit counts, and not merging beyond that. For fragmented freespace, as normal, perhaps that would be a better memory savings? But this fixes the immediate problem and seems worth merging to avoid bad situations such as e2fsck corrupting a perfectly good 32T filesystem... -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html