From: Jan Kara <jack@xxxxxxx> commit 163f0ec1df33cf468509ff38cbcbb5eb0d7fac60 upstream. 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@xxxxxxxxxx/ Signed-off-by: Jan Kara <jack@xxxxxxx> Link: https://lore.kernel.org/r/20210222171626.21884-1-jack@xxxxxxx Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/ext4/xattr.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -1480,6 +1480,9 @@ ext4_xattr_inode_cache_find(struct inode if (!ce) return NULL; + WARN_ON_ONCE(ext4_handle_valid(journal_current_handle()) && + !(current->flags & PF_MEMALLOC_NOFS)); + ea_data = ext4_kvmalloc(value_len, GFP_NOFS); if (!ea_data) { mb_cache_entry_put(ea_inode_cache, ce); @@ -2346,6 +2349,7 @@ ext4_xattr_set_handle(handle_t *handle, error = -ENOSPC; goto cleanup; } + WARN_ON_ONCE(!(current->flags & PF_MEMALLOC_NOFS)); } error = ext4_reserve_inode_write(handle, inode, &is.iloc);
