From 511a1303c9cf9663c7d4312e3a0693319f41095b Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Mon, 13 Feb 2023 08:37:59 +0800 Subject: [PATCH] fs: btrfs: limit the mapped length to the original length [BUG] There is a bug report that btrfs driver caused hang during file read: This breaks btrfs on the HiFive Unmatched. => pci enum PCIE-0: Link up (Gen1-x8, Bus0) => nvme scan => load nvme 0:2 0x8c000000 /boot/dtb/sifive/hifive-unmatched-a00.dtb [hangs] [CAUSE] The reporter provided some debug output: read_extent_data: cur=615817216, orig_len=16384, cur_len=16384 read_extent_data: btrfs_map_block: cur_len=479944704; ret=0 read_extent_data: ret=0 read_extent_data: cur=615833600, orig_len=4096, cur_len=4096 read_extent_data: btrfs_map_block: cur_len=479928320; ret=0 Note the second and the last line, the @cur_len is 450+MiB, which is almost a chunk size. And inside __btrfs_map_block(), we limits the returned value to stripe length, but that's depending on the chunk type: if (map->type & (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID1C3 | BTRFS_BLOCK_GROUP_RAID1C4 | BTRFS_BLOCK_GROUP_RAID5 | BTRFS_BLOCK_GROUP_RAID6 | BTRFS_BLOCK_GROUP_RAID10 | BTRFS_BLOCK_GROUP_DUP)) { /* we limit the length of each bio to what fits in a stripe */ *length = min_t(u64, ce->size - offset, map->stripe_len - stripe_offset); } else { *length = ce->size - offset; } This means, if the chunk is SINGLE profile, then we don't limit the returned length at all, and even for other profiles, we can still return a length much larger than the requested one. [FIX] Properly clamp the returned length, preventing it from returning a much larger range than expected. Reported-by: Andreas Schwab Signed-off-by: Qu Wenruo --- fs/btrfs/volumes.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 4aaaeab..7d4095d 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -956,6 +956,7 @@ int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw, struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree; struct cache_extent *ce; struct map_lookup *map; + u64 orig_len = *length; u64 offset; u64 stripe_offset; u64 *raid_map = NULL; @@ -1047,6 +1048,7 @@ again: } else { *length = ce->size - offset; } + *length = min_t(u64, *length, orig_len); if (!multi_ret) goto out; -- 2.7.4