From e8fd2e459649ab5105cc627018dd25ea395719de Mon Sep 17 00:00:00 2001
From: Qu Wenruo <wqu@suse.com>
Date: Mon, 18 Mar 2019 10:37:22 +0800
Patch-mainline: v5.2-rc1
Git-commit: 10995c0491204c861948c9850939a7f4e90760a4
References: bsc#1129497 bsc#1134651
Subject: [PATCH] btrfs: reloc: Fix NULL pointer dereference due to expanded
reloc_root lifespan
Commit 514e70150b60 ("btrfs: relocation: Delay reloc tree deletion after
merge_reloc_roots()") expands the life span of root->reloc_root.
This breaks certain check on fs_info->reloc_ctl.
Before that commit, if we have a root with valid reloc_root, then it's
ensured to have fs_info->reloc_ctl.
But now since reloc_root doesn't always mean a valid fs_info->reloc_ctl,
such check is unreliable and can cause the following NULL pointer
dereference:
BUG: unable to handle kernel NULL pointer dereference at 00000000000005c1
IP: btrfs_reloc_pre_snapshot+0x20/0x50 [btrfs]
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
CPU: 0 PID: 10379 Comm: snapperd Not tainted 4.12.14-lp150.12.53-default #1 openSUSE Leap 15.0
Call Trace:
create_pending_snapshot+0xd7/0xfc0 [btrfs]
create_pending_snapshots+0x8e/0xb0 [btrfs]
btrfs_commit_transaction+0x2ac/0x8f0 [btrfs]
btrfs_mksubvol+0x561/0x570 [btrfs]
btrfs_ioctl_snap_create_transid+0x189/0x190 [btrfs]
btrfs_ioctl_snap_create_v2+0x102/0x150 [btrfs]
btrfs_ioctl+0x5c9/0x1e60 [btrfs]
do_vfs_ioctl+0x90/0x5f0
SyS_ioctl+0x74/0x80
do_syscall_64+0x7b/0x150
entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x7fd7cdab8467
Fix it by explicitly checking fs_info->reloc_ctl other than using the
implied root->reloc_root.
Fixes: 514e70150b60 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots()")
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
fs/btrfs/relocation.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index ddf028509931..351fa506dc9b 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4667,14 +4667,12 @@ int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans,
void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending,
u64 *bytes_to_reserve)
{
- struct btrfs_root *root;
- struct reloc_control *rc;
+ struct btrfs_root *root = pending->root;
+ struct reloc_control *rc = root->fs_info->reloc_ctl;
- root = pending->root;
- if (!root->reloc_root)
+ if (!root->reloc_root || !rc)
return;
- rc = root->fs_info->reloc_ctl;
if (!rc->merge_reloc_tree)
return;
@@ -4703,10 +4701,10 @@ int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
struct btrfs_root *root = pending->root;
struct btrfs_root *reloc_root;
struct btrfs_root *new_root;
- struct reloc_control *rc;
+ struct reloc_control *rc = root->fs_info->reloc_ctl;
int ret;
- if (!root->reloc_root)
+ if (!root->reloc_root || !rc)
return 0;
rc = root->fs_info->reloc_ctl;
--
2.21.0