From: "Darrick J. Wong" djwong@kernel.org
[ Upstream commit 95ff0363f3f6ae70c21a0f2b0603e54438e5988b ]
The kernel build robot reported a UAF error while running xfs/433 (edited somewhat for brevity):
BUG: KASAN: use-after-free in xfs_attr3_node_inactive (fs/xfs/xfs_attr_inactive.c:214) xfs Read of size 4 at addr ffff88820ac2bd44 by task kworker/0:2/139
CPU: 0 PID: 139 Comm: kworker/0:2 Tainted: G S 5.19.0-rc2-00004-g7cf2b0f9611b #1 Hardware name: Hewlett-Packard p6-1451cx/2ADA, BIOS 8.15 02/05/2013 Workqueue: xfs-inodegc/sdb4 xfs_inodegc_worker [xfs] Call Trace: <TASK> dump_stack_lvl (lib/dump_stack.c:107 (discriminator 1)) print_address_description+0x1f/0x200 print_report.cold (mm/kasan/report.c:430) kasan_report (mm/kasan/report.c:162 mm/kasan/report.c:493) xfs_attr3_node_inactive (fs/xfs/xfs_attr_inactive.c:214) xfs xfs_attr3_root_inactive (fs/xfs/xfs_attr_inactive.c:296) xfs xfs_attr_inactive (fs/xfs/xfs_attr_inactive.c:371) xfs xfs_inactive (fs/xfs/xfs_inode.c:1781) xfs xfs_inodegc_worker (fs/xfs/xfs_icache.c:1837 fs/xfs/xfs_icache.c:1860) xfs process_one_work worker_thread kthread ret_from_fork </TASK>
Allocated by task 139: kasan_save_stack (mm/kasan/common.c:39) __kasan_slab_alloc (mm/kasan/common.c:45 mm/kasan/common.c:436 mm/kasan/common.c:469) kmem_cache_alloc (mm/slab.h:750 mm/slub.c:3214 mm/slub.c:3222 mm/slub.c:3229 mm/slub.c:3239) _xfs_buf_alloc (include/linux/instrumented.h:86 include/linux/atomic/atomic-instrumented.h:41 fs/xfs/xfs_buf.c:232) xfs xfs_buf_get_map (fs/xfs/xfs_buf.c:660) xfs xfs_buf_read_map (fs/xfs/xfs_buf.c:777) xfs xfs_trans_read_buf_map (fs/xfs/xfs_trans_buf.c:289) xfs xfs_da_read_buf (fs/xfs/libxfs/xfs_da_btree.c:2652) xfs xfs_da3_node_read (fs/xfs/libxfs/xfs_da_btree.c:392) xfs xfs_attr3_root_inactive (fs/xfs/xfs_attr_inactive.c:272) xfs xfs_attr_inactive (fs/xfs/xfs_attr_inactive.c:371) xfs xfs_inactive (fs/xfs/xfs_inode.c:1781) xfs xfs_inodegc_worker (fs/xfs/xfs_icache.c:1837 fs/xfs/xfs_icache.c:1860) xfs process_one_work worker_thread kthread ret_from_fork
Freed by task 139: kasan_save_stack (mm/kasan/common.c:39) kasan_set_track (mm/kasan/common.c:45) kasan_set_free_info (mm/kasan/generic.c:372) __kasan_slab_free (mm/kasan/common.c:368 mm/kasan/common.c:328 mm/kasan/common.c:374) kmem_cache_free (mm/slub.c:1753 mm/slub.c:3507 mm/slub.c:3524) xfs_buf_rele (fs/xfs/xfs_buf.c:1040) xfs xfs_attr3_node_inactive (fs/xfs/xfs_attr_inactive.c:210) xfs xfs_attr3_root_inactive (fs/xfs/xfs_attr_inactive.c:296) xfs xfs_attr_inactive (fs/xfs/xfs_attr_inactive.c:371) xfs xfs_inactive (fs/xfs/xfs_inode.c:1781) xfs xfs_inodegc_worker (fs/xfs/xfs_icache.c:1837 fs/xfs/xfs_icache.c:1860) xfs process_one_work worker_thread kthread ret_from_fork
I reproduced this for my own satisfaction, and got the same report, along with an extra morsel:
The buggy address belongs to the object at ffff88802103a800 which belongs to the cache xfs_buf of size 432 The buggy address is located 396 bytes inside of 432-byte region [ffff88802103a800, ffff88802103a9b0)
I tracked this code down to:
error = xfs_trans_get_buf(*trans, mp->m_ddev_targp, child_blkno, XFS_FSB_TO_BB(mp, mp->m_attr_geo->fsbcount), 0, &child_bp); if (error) return error; error = bp->b_error;
That doesn't look right -- I think this should be dereferencing child_bp, not bp. Looking through the codebase history, I think this was added by commit 2911edb653b9 ("xfs: remove the mappedbno argument to xfs_da_get_buf"), which replaced a call to xfs_da_get_buf with the current call to xfs_trans_get_buf. Not sure why we trans_brelse'd @bp earlier in the function, but I'm guessing it's to avoid pinning too many buffers in memory while we inactivate the bottom of the attr tree. Hence we now have to get the buffer back.
I /think/ this was supposed to check child_bp->b_error and fail the rest of the invalidation if child_bp had experienced any kind of IO or corruption error. I bet the xfs_da3_node_read earlier in the loop will catch most cases of incoming on-disk corruption which makes this check mostly moot unless someone corrupts the buffer and the AIL pushes it out to disk while the buffer's unlocked.
In the first case we'll never get to the bad check, and in the second case the AIL will shut down the log, at which point there's no reason to check b_error. Remove the check, and null out @bp to avoid this problem in the future.
Cc: hch@lst.de Reported-by: kernel test robot oliver.sang@intel.com Fixes: 2911edb653b9 ("xfs: remove the mappedbno argument to xfs_da_get_buf") Signed-off-by: Darrick J. Wong djwong@kernel.org Reviewed-by: Dave Chinner dchinner@redhat.com Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Leah Rumancik leah.rumancik@gmail.com Acked-by: Chandan Babu R chandanbabu@kernel.org --- fs/xfs/xfs_attr_inactive.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/fs/xfs/xfs_attr_inactive.c b/fs/xfs/xfs_attr_inactive.c index 2b5da6218977..2afa6d9a7f8f 100644 --- a/fs/xfs/xfs_attr_inactive.c +++ b/fs/xfs/xfs_attr_inactive.c @@ -158,6 +158,7 @@ xfs_attr3_node_inactive( } child_fsb = be32_to_cpu(ichdr.btree[0].before); xfs_trans_brelse(*trans, bp); /* no locks for later trans */ + bp = NULL;
/* * If this is the node level just above the leaves, simply loop @@ -211,12 +212,8 @@ xfs_attr3_node_inactive( &child_bp); if (error) return error; - error = bp->b_error; - if (error) { - xfs_trans_brelse(*trans, child_bp); - return error; - } xfs_trans_binval(*trans, child_bp); + child_bp = NULL;
/* * If we're not done, re-read the parent to get the next @@ -233,6 +230,7 @@ xfs_attr3_node_inactive( bp->b_addr); child_fsb = be32_to_cpu(phdr.btree[i + 1].before); xfs_trans_brelse(*trans, bp); + bp = NULL; } /* * Atomically commit the whole invalidate stuff.