[PATCH] stackdepot: respect __GFP_NOLOCKDEP allocation flag

Andrey Ryabinin
2024-04-18T14:12:52Z

If stack_depot_save_flags() allocates memory it always drops
__GFP_NOLOCKDEP flag. So when KASAN tries to track __GFP_NOLOCKDEP
allocation we may end up with lockdep splat like bellow:

======================================================
WARNING: possible circular locking dependency detected
6.9.0-rc3+ #49 Not tainted
------------------------------------------------------
kswapd0/149 is trying to acquire lock:
ffff88811346a920
(&xfs_nondir_ilock_class){++++}-{4:4}, at: xfs_reclaim_inode+0x3ac/0x590
[xfs]

but task is already holding lock:
ffffffff8bb33100 (fs_reclaim){+.+.}-{0:0}, at:
balance_pgdat+0x5d9/0xad0

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:
-> #1 (fs_reclaim){+.+.}-{0:0}:
__lock_acquire+0x7da/0x1030
lock_acquire+0x15d/0x400
fs_reclaim_acquire+0xb5/0x100
prepare_alloc_pages.constprop.0+0xc5/0x230
__alloc_pages+0x12a/0x3f0
alloc_pages_mpol+0x175/0x340
stack_depot_save_flags+0x4c5/0x510
kasan_save_stack+0x30/0x40
kasan_save_track+0x10/0x30
__kasan_slab_alloc+0x83/0x90
kmem_cache_alloc+0x15e/0x4a0
__alloc_object+0x35/0x370
__create_object+0x22/0x90
__kmalloc_node_track_caller+0x477/0x5b0
krealloc+0x5f/0x110
xfs_iext_insert_raw+0x4b2/0x6e0 [xfs]
xfs_iext_insert+0x2e/0x130 [xfs]
xfs_iread_bmbt_block+0x1a9/0x4d0 [xfs]
xfs_btree_visit_block+0xfb/0x290 [xfs]
xfs_btree_visit_blocks+0x215/0x2c0 [xfs]
xfs_iread_extents+0x1a2/0x2e0 [xfs]
xfs_buffered_write_iomap_begin+0x376/0x10a0 [xfs]
iomap_iter+0x1d1/0x2d0
iomap_file_buffered_write+0x120/0x1a0
xfs_file_buffered_write+0x128/0x4b0 [xfs]
vfs_write+0x675/0x890
ksys_write+0xc3/0x160
do_syscall_64+0x94/0x170
entry_SYSCALL_64_after_hwframe+0x71/0x79

Always preserve __GFP_NOLOCKDEP to fix this.

Fixes: cd11016e5f52 ("mm, kasan: stackdepot implementation. Enable stackdepot for SLAB")
Reported-by: Xiubo Li <xiubli@redhat.com>
Closes: https://lore.kernel.org/all/a0caa289-ca02-48eb-9bf2-d86fd47b71f4@redhat.com/
Reported-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Closes: https://lore.kernel.org/all/f9ff999a-e170-b66b-7caf-293f2b147ac2@opensource.wdc.com/
Suggested-by: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
---
lib/stackdepot.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 68c97387aa54..cd8f23455285 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -627,10 +627,10 @@ depot_stack_handle_t stack_depot_save_flags(unsigned long *entries,
/*
* Zero out zone modifiers, as we don't have specific zone
* requirements. Keep the flags related to allocation in atomic
- * contexts and I/O.
+ * contexts, I/O, nolockdep.
*/
alloc_flags &= ~GFP_ZONEMASK;
- alloc_flags &= (GFP_ATOMIC | GFP_KERNEL);
+ alloc_flags &= (GFP_ATOMIC | GFP_KERNEL | __GFP_NOLOCKDEP);
alloc_flags |= __GFP_NOWARN;
page = alloc_pages(alloc_flags, DEPOT_POOL_ORDER);
if (page)
--
2.43.2