Re: [PATCH AUTOSEL 5.11 03/44] ext4: add reclaim checks to xattr code
From: Jan Kara <jack@suse.cz>
Date: 2021-03-25 14:31:19
Also in:
lkml, stable
Sasha, just be aware that this commit was added to help tracking down a particular syzbot report. As such there's no point in carrying it in -stable but there's no big harm either... Just one patch more. Honza On Thu 25-03-21 07:24:18, Sasha Levin wrote:
quoted hunk ↗ jump to hunk
From: Jan Kara <jack@suse.cz> [ Upstream commit 163f0ec1df33cf468509ff38cbcbb5eb0d7fac60 ] Syzbot is reporting that ext4 can enter fs reclaim from kvmalloc() while the transaction is started like: fs_reclaim_acquire+0x117/0x150 mm/page_alloc.c:4340 might_alloc include/linux/sched/mm.h:193 [inline] slab_pre_alloc_hook mm/slab.h:493 [inline] slab_alloc_node mm/slub.c:2817 [inline] __kmalloc_node+0x5f/0x430 mm/slub.c:4015 kmalloc_node include/linux/slab.h:575 [inline] kvmalloc_node+0x61/0xf0 mm/util.c:587 kvmalloc include/linux/mm.h:781 [inline] ext4_xattr_inode_cache_find fs/ext4/xattr.c:1465 [inline] ext4_xattr_inode_lookup_create fs/ext4/xattr.c:1508 [inline] ext4_xattr_set_entry+0x1ce6/0x3780 fs/ext4/xattr.c:1649 ext4_xattr_ibody_set+0x78/0x2b0 fs/ext4/xattr.c:2224 ext4_xattr_set_handle+0x8f4/0x13e0 fs/ext4/xattr.c:2380 ext4_xattr_set+0x13a/0x340 fs/ext4/xattr.c:2493 This should be impossible since transaction start sets PF_MEMALLOC_NOFS. Add some assertions to the code to catch if something isn't working as expected early. Link: https://lore.kernel.org/linux-ext4/000000000000563a0205bafb7970@google.com/ (local) Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20210222171626.21884-1-jack@suse.cz (local) Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Sasha Levin <sashal@kernel.org> --- fs/ext4/xattr.c | 4 ++++ 1 file changed, 4 insertions(+)diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c index 372208500f4e..083c95126781 100644 --- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c@@ -1462,6 +1462,9 @@ ext4_xattr_inode_cache_find(struct inode *inode, const void *value, if (!ce) return NULL; + WARN_ON_ONCE(ext4_handle_valid(journal_current_handle()) && + !(current->flags & PF_MEMALLOC_NOFS)); + ea_data = kvmalloc(value_len, GFP_KERNEL); if (!ea_data) { mb_cache_entry_put(ea_inode_cache, ce);@@ -2327,6 +2330,7 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index, error = -ENOSPC; goto cleanup; } + WARN_ON_ONCE(!(current->flags & PF_MEMALLOC_NOFS)); } error = ext4_reserve_inode_write(handle, inode, &is.iloc);-- 2.30.1
-- Jan Kara [off-list ref] SUSE Labs, CR