From: Dongliang Mu Date: Thu, 3 Mar 2022 14:40:27 +0000 (+0800) Subject: btrfs: don't access possibly stale fs_info data in device_list_add X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=83772314e1e0a5232823651e44a77a33857eafba;p=linux.git btrfs: don't access possibly stale fs_info data in device_list_add [ Upstream commit 79c9234ba596e903907de20573fd4bcc85315b06 ] Syzbot reported a possible use-after-free in printing information in device_list_add. Very similar with the bug fixed by commit 0697d9a61099 ("btrfs: don't access possibly stale fs_info data for printing duplicate device"), but this time the use occurs in btrfs_info_in_rcu. Call Trace: kasan_report.cold+0x83/0xdf mm/kasan/report.c:459 btrfs_printk+0x395/0x425 fs/btrfs/super.c:244 device_list_add.cold+0xd7/0x2ed fs/btrfs/volumes.c:957 btrfs_scan_one_device+0x4c7/0x5c0 fs/btrfs/volumes.c:1387 btrfs_control_ioctl+0x12a/0x2d0 fs/btrfs/super.c:2409 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae Fix this by modifying device->fs_info to NULL too. Reported-and-tested-by: syzbot+82650a4e0ed38f218363@syzkaller.appspotmail.com CC: stable@vger.kernel.org # 4.19+ Signed-off-by: Dongliang Mu Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index cec54c6e1cdd6..89ce0b449c22a 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -955,6 +955,11 @@ static noinline struct btrfs_device *device_list_add(const char *path, /* * We are going to replace the device path for a given devid, * make sure it's the same device if the device is mounted + * + * NOTE: the device->fs_info may not be reliable here so pass + * in a NULL to message helpers instead. This avoids a possible + * use-after-free when the fs_info and fs_info->sb are already + * torn down. */ if (device->bdev) { int error; @@ -968,12 +973,6 @@ static noinline struct btrfs_device *device_list_add(const char *path, if (device->bdev->bd_dev != path_dev) { mutex_unlock(&fs_devices->device_list_mutex); - /* - * device->fs_info may not be reliable here, so - * pass in a NULL instead. This avoids a - * possible use-after-free when the fs_info and - * fs_info->sb are already torn down. - */ btrfs_warn_in_rcu(NULL, "duplicate device %s devid %llu generation %llu scanned by %s (%d)", path, devid, found_transid, @@ -981,7 +980,7 @@ static noinline struct btrfs_device *device_list_add(const char *path, task_pid_nr(current)); return ERR_PTR(-EEXIST); } - btrfs_info_in_rcu(device->fs_info, + btrfs_info_in_rcu(NULL, "devid %llu device path %s changed to %s scanned by %s (%d)", devid, rcu_str_deref(device->name), path, current->comm,