On 2024/6/19 19:01, Greg KH wrote:

On Mon, Jun 17, 2024 at 09:37:01AM +0800, Baokun Li wrote:

...

Hi Sasha,

Thanks for adapting this patch to the stable branch. Just one nit.

On 2024/6/16 10:05, Sasha Levin wrote:

...

This is a note to let you know that I've just added the patch titled

  ext4: fix slab-out-of-bounds in ext4_mb_find_good_group_avg_frag_lists()

to the 6.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: ext4-fix-slab-out-of-bounds-in-ext4_mb_find_good_gro.patch and it can be found in the queue-6.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

commit 84cee2d2394a43766dd2990edac8a4a05817ef7b Author: Baokun Li libaokun1@huawei.com Date: Tue Mar 19 19:33:20 2024 +0800

  ext4: fix slab-out-of-bounds in ext4_mb_find_good_group_avg_frag_lists()
  [ Upstream commit 13df4d44a3aaabe61cd01d277b6ee23ead2a5206 ]
  We can trigger a slab-out-of-bounds with the following commands:
      mkfs.ext4 -F /dev/$disk 10G
      mount /dev/$disk /tmp/test
      echo 2147483647 > /sys/fs/ext4/$disk/mb_group_prealloc
      echo test > /tmp/test/file && sync
  ==================================================================
  BUG: KASAN: slab-out-of-bounds in ext4_mb_find_good_group_avg_frag_lists+0x8a/0x200 [ext4]
  Read of size 8 at addr ffff888121b9d0f0 by task kworker/u2:0/11
  CPU: 0 PID: 11 Comm: kworker/u2:0 Tainted: GL 6.7.0-next-20240118 #521
  Call Trace:
   dump_stack_lvl+0x2c/0x50
   kasan_report+0xb6/0xf0
   ext4_mb_find_good_group_avg_frag_lists+0x8a/0x200 [ext4]
   ext4_mb_regular_allocator+0x19e9/0x2370 [ext4]
   ext4_mb_new_blocks+0x88a/0x1370 [ext4]
   ext4_ext_map_blocks+0x14f7/0x2390 [ext4]
   ext4_map_blocks+0x569/0xea0 [ext4]
   ext4_do_writepages+0x10f6/0x1bc0 [ext4]
  [...]
  ==================================================================
  The flow of issue triggering is as follows:
  // Set s_mb_group_prealloc to 2147483647 via sysfs
  ext4_mb_new_blocks
    ext4_mb_normalize_request
      ext4_mb_normalize_group_request
        ac->ac_g_ex.fe_len = EXT4_SB(sb)->s_mb_group_prealloc
    ext4_mb_regular_allocator
      ext4_mb_choose_next_group
        ext4_mb_choose_next_group_best_avail
          mb_avg_fragment_size_order
            order = fls(len) - 2 = 29
          ext4_mb_find_good_group_avg_frag_lists
            frag_list = &sbi->s_mb_avg_fragment_size[order]
            if (list_empty(frag_list)) // Trigger SOOB!
  At 4k block size, the length of the s_mb_avg_fragment_size list is 14,
  but an oversized s_mb_group_prealloc is set, causing slab-out-of-bounds
  to be triggered by an attempt to access an element at index 29.
  Add a new attr_id attr_clusters_in_group with values in the range
  [0, sbi->s_clusters_per_group] and declare mb_group_prealloc as
  that type to fix the issue. In addition avoid returning an order
  from mb_avg_fragment_size_order() greater than MB_NUM_ORDERS(sb)
  and reduce some useless loops.
  Fixes: 7e170922f06b ("ext4: Add allocation criteria 1.5 (CR1_5)")
  CC: stable@vger.kernel.org
  Signed-off-by: Baokun Li <libaokun1@huawei.com>
  Reviewed-by: Jan Kara <jack@suse.cz>
  Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
  Link: https://lore.kernel.org/r/20240319113325.3110393-5-libaokun1@huawei.com
  Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 714f83632e3f9..66b5a68b0254e 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -831,6 +831,8 @@ static int mb_avg_fragment_size_order(struct super_block *sb, ext4_grpblk_t len) return 0; if (order == MB_NUM_ORDERS(sb)) order--;

• if (WARN_ON_ONCE(order > MB_NUM_ORDERS(sb)))

• order = MB_NUM_ORDERS(sb) - 1;
  

  return order; }

@@ -1008,6 +1010,8 @@ static void ext4_mb_choose_next_group_best_avail(struct ext4_allocation_context * goal length. */ order = fls(ac->ac_g_ex.fe_len) - 1;

• if (WARN_ON_ONCE(order - 1 > MB_NUM_ORDERS(ac->ac_sb)))

• order = MB_NUM_ORDERS(ac->ac_sb);
  

  min_order = order - sbi->s_mb_best_avail_max_trim_order; if (min_order < 0) min_order = 0;

diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c index 295ea9a32de91..ca66e33f61815 100644 --- a/fs/ext4/sysfs.c +++ b/fs/ext4/sysfs.c @@ -29,6 +29,7 @@ typedef enum { attr_trigger_test_error, attr_first_error_time, attr_last_error_time,

• attr_clusters_in_group, attr_feature, attr_pointer_ui, attr_pointer_ul,

@@ -207,13 +208,14 @@ EXT4_ATTR_FUNC(sra_exceeded_retry_limit, 0444); EXT4_ATTR_OFFSET(inode_readahead_blks, 0644, inode_readahead, ext4_sb_info, s_inode_readahead_blks); +EXT4_ATTR_OFFSET(mb_group_prealloc, 0644, clusters_in_group,

•  ext4_sb_info, s_mb_group_prealloc);
  

  EXT4_RW_ATTR_SBI_UI(inode_goal, s_inode_goal); EXT4_RW_ATTR_SBI_UI(mb_stats, s_mb_stats); EXT4_RW_ATTR_SBI_UI(mb_max_to_scan, s_mb_max_to_scan); EXT4_RW_ATTR_SBI_UI(mb_min_to_scan, s_mb_min_to_scan); EXT4_RW_ATTR_SBI_UI(mb_order2_req, s_mb_order2_reqs); EXT4_RW_ATTR_SBI_UI(mb_stream_req, s_mb_stream_request);

-EXT4_RW_ATTR_SBI_UI(mb_group_prealloc, s_mb_group_prealloc); EXT4_RW_ATTR_SBI_UI(mb_max_linear_groups, s_mb_max_linear_groups); EXT4_RW_ATTR_SBI_UI(extent_max_zeroout_kb, s_extent_max_zeroout_kb); EXT4_ATTR(trigger_fs_error, 0200, trigger_test_error); @@ -376,6 +378,7 @@ static ssize_t ext4_generic_attr_show(struct ext4_attr *a, switch (a->attr_id) { case attr_inode_readahead:

• case attr_clusters_in_group: case attr_pointer_ui: if (a->attr_ptr == ptr_ext4_super_block_offset) return sysfs_emit(buf, "%u\n", le32_to_cpup(ptr));

@@ -459,6 +462,14 @@ static ssize_t ext4_attr_store(struct kobject *kobj, else *((unsigned int *) ptr) = t; return len;

• case attr_clusters_in_group:

Since commit f536808adcc3 "ext4: refactor out ext4_generic_attr_store()" is not backported to stable, the following judgement needs to be added here:

if (!ptr)
	return 0;

The patch for the 6.6-stable tree has the same problem.

Thanks, I've dropped this from both queues now, can you resend it with a fixed up version?

thanks,

greg k-h

Okay. I'll send out the corrected version soon.