From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3D4131D0BAA; Tue, 8 Oct 2024 12:34:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728390867; cv=none; b=lcRUtP1pwaKjppmkK8SHCXDSfUQ4Z3L3SwVFDs1i9Dngq3LVRTL0/6aKtQXvqXtHj8kt1YXdQOmPXNZMWUMIsZc49SFD6dALHZVTJ0Vqb/hUNnvWj6gsR7WacGwupaa0fTPoGxHRUhr+faV7IIwL1jdC7Z4Naw/NCJzxEPE27WY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728390867; c=relaxed/simple; bh=bhQm8Bpz882fX+ShLyXZ6rKNtF3bWMrGdf3oCgGC9z0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PU6tU4WaM4BhAA01YKg2XqR0ie75fqN8r/bkstkiihWdoC2Kzly12edixQz4Omb9uBrLqt1081eobKZTn8xoPQa1Oq7dKz2S26kX5rxI0RLJvdXEh0e9FNxELI1cqYXTOWy/Q19DlK6P9+V3LtgFV0dnm/lPDJutT3gL1vWjB0U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=i1uJ7ft8; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="i1uJ7ft8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9FA79C4CEC7; Tue, 8 Oct 2024 12:34:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1728390867; bh=bhQm8Bpz882fX+ShLyXZ6rKNtF3bWMrGdf3oCgGC9z0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=i1uJ7ft8Hct/BcKsbTNMDWYPwWrCJPFRotKq+OpqHXGV2sk7nFIzEgkEX1UEevcMU 4itzvPQR6/5iXEPzQOFg+KCrc5cvOPsiAXw495iOf1DFT09ZJvf3lzXCFOHYvqoKKo 1Vycs/rvwaDwPHKqpjKP06Vm93qOg85Cc1LvrvkI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+283673dbc38527ef9f3d@syzkaller.appspotmail.com, Josef Bacik , Qu Wenruo , David Sterba Subject: [PATCH 6.10 417/482] btrfs: fix a NULL pointer dereference when failed to start a new trasacntion Date: Tue, 8 Oct 2024 14:08:00 +0200 Message-ID: <20241008115704.812651727@linuxfoundation.org> X-Mailer: git-send-email 2.46.2 In-Reply-To: <20241008115648.280954295@linuxfoundation.org> References: <20241008115648.280954295@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Qu Wenruo commit c3b47f49e83197e8dffd023ec568403bcdbb774b upstream. [BUG] Syzbot reported a NULL pointer dereference with the following crash: FAULT_INJECTION: forcing a failure. start_transaction+0x830/0x1670 fs/btrfs/transaction.c:676 prepare_to_relocate+0x31f/0x4c0 fs/btrfs/relocation.c:3642 relocate_block_group+0x169/0xd20 fs/btrfs/relocation.c:3678 ... BTRFS info (device loop0): balance: ended with status: -12 Oops: general protection fault, probably for non-canonical address 0xdffffc00000000cc: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000660-0x0000000000000667] RIP: 0010:btrfs_update_reloc_root+0x362/0xa80 fs/btrfs/relocation.c:926 Call Trace: commit_fs_roots+0x2ee/0x720 fs/btrfs/transaction.c:1496 btrfs_commit_transaction+0xfaf/0x3740 fs/btrfs/transaction.c:2430 del_balance_item fs/btrfs/volumes.c:3678 [inline] reset_balance_state+0x25e/0x3c0 fs/btrfs/volumes.c:3742 btrfs_balance+0xead/0x10c0 fs/btrfs/volumes.c:4574 btrfs_ioctl_balance+0x493/0x7c0 fs/btrfs/ioctl.c:3673 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f [CAUSE] The allocation failure happens at the start_transaction() inside prepare_to_relocate(), and during the error handling we call unset_reloc_control(), which makes fs_info->balance_ctl to be NULL. Then we continue the error path cleanup in btrfs_balance() by calling reset_balance_state() which will call del_balance_item() to fully delete the balance item in the root tree. However during the small window between set_reloc_contrl() and unset_reloc_control(), we can have a subvolume tree update and created a reloc_root for that subvolume. Then we go into the final btrfs_commit_transaction() of del_balance_item(), and into btrfs_update_reloc_root() inside commit_fs_roots(). That function checks if fs_info->reloc_ctl is in the merge_reloc_tree stage, but since fs_info->reloc_ctl is NULL, it results a NULL pointer dereference. [FIX] Just add extra check on fs_info->reloc_ctl inside btrfs_update_reloc_root(), before checking fs_info->reloc_ctl->merge_reloc_tree. That DEAD_RELOC_TREE handling is to prevent further modification to the reloc tree during merge stage, but since there is no reloc_ctl at all, we do not need to bother that. Reported-by: syzbot+283673dbc38527ef9f3d@syzkaller.appspotmail.com Link: https://lore.kernel.org/linux-btrfs/66f6bfa7.050a0220.38ace9.0019.GAE@google.com/ CC: stable@vger.kernel.org # 4.19+ Reviewed-by: Josef Bacik Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/relocation.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -922,7 +922,7 @@ int btrfs_update_reloc_root(struct btrfs btrfs_grab_root(reloc_root); /* root->reloc_root will stay until current relocation finished */ - if (fs_info->reloc_ctl->merge_reloc_tree && + if (fs_info->reloc_ctl && fs_info->reloc_ctl->merge_reloc_tree && btrfs_root_refs(root_item) == 0) { set_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state); /*