This is a note to let you know that I've just added the patch titled
ext4: add reclaim checks to xattr code
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ext4-add-reclaim-checks-to-xattr-code.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 163f0ec1df33cf468509ff38cbcbb5eb0d7fac60 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@xxxxxxx>
Date: Mon, 22 Feb 2021 18:16:26 +0100
Subject: ext4: add reclaim checks to xattr code
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
@@ -1476,6 +1476,9 @@ 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);
@@ -2342,6 +2345,7 @@ 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);
Patches currently in stable-queue which might be from jack@xxxxxxx are
queue-5.4/ext4-add-reclaim-checks-to-xattr-code.patch
