[PATCH 5.10 CANDIDATE 01/11] xfs: use kmem_cache_free() for kmem_cache objects

Amir Goldstein
2022-06-17T10:07:32Z

From: Rustam Kovhaev <rkovhaev@gmail.com>

commit c30a0cbd07ecc0eec7b3cd568f7b1c7bb7913f93 upstream.

For kmalloc() allocations SLOB prepends the blocks with a 4-byte header,
and it puts the size of the allocated blocks in that header.
Blocks allocated with kmem_cache_alloc() allocations do not have that
header.

SLOB explodes when you allocate memory with kmem_cache_alloc() and then
try to free it with kfree() instead of kmem_cache_free().
SLOB will assume that there is a header when there is none, read some
garbage to size variable and corrupt the adjacent objects, which
eventually leads to hang or panic.

Let's make XFS work with SLOB by using proper free function.

Fixes: 9749fee83f38 ("xfs: enable the xfs_defer mechanism to process extents to free")
Signed-off-by: Rustam Kovhaev <rkovhaev@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/xfs/xfs_extfree_item.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_extfree_item.c b/fs/xfs/xfs_extfree_item.c
index 5c0395256bd1..11474770d630 100644
--- a/fs/xfs/xfs_extfree_item.c
+++ b/fs/xfs/xfs_extfree_item.c
@@ -482,7 +482,7 @@ xfs_extent_free_finish_item(
free->xefi_startblock,
free->xefi_blockcount,
&free->xefi_oinfo, free->xefi_skip_discard);
- kmem_free(free);
+ kmem_cache_free(xfs_bmap_free_item_zone, free);
return error;
}

@@ -502,7 +502,7 @@ xfs_extent_free_cancel_item(
struct xfs_extent_free_item *free;

free = container_of(item, struct xfs_extent_free_item, xefi_list);
- kmem_free(free);
+ kmem_cache_free(xfs_bmap_free_item_zone, free);
}

const struct xfs_defer_op_type xfs_extent_free_defer_type = {
@@ -564,7 +564,7 @@ xfs_agfl_free_finish_item(
extp->ext_len = free->xefi_blockcount;
efdp->efd_next_extent++;

- kmem_free(free);
+ kmem_cache_free(xfs_bmap_free_item_zone, free);
return error;
}

--
2.25.1