On Tue, Jun 30, 2020 at 02:53:02PM -0400, Josef Bacik wrote:
> Eric reported an issue where mounting -o recovery with a fuzzed fs
> resulted in a kernel panic. This is because we tried to free the tree
> node, except it was an error from the read. Fix this by properly
> resetting the tree_root->node == NULL in this case. The panic was the
> following
>
> BTRFS warning (device loop0): failed to read tree root
> BUG: kernel NULL pointer dereference, address: 000000000000001f
> RIP: 0010:free_extent_buffer+0xe/0x90 [btrfs]
> Call Trace:
> free_root_extent_buffers.part.0+0x11/0x30 [btrfs]
> free_root_pointers+0x1a/0xa2 [btrfs]
> open_ctree+0x1776/0x18a5 [btrfs]
> btrfs_mount_root.cold+0x13/0xfa [btrfs]
> ? selinux_fs_context_parse_param+0x37/0x80
> legacy_get_tree+0x27/0x40
> vfs_get_tree+0x25/0xb0
> fc_mount+0xe/0x30
> vfs_kern_mount.part.0+0x71/0x90
> btrfs_mount+0x147/0x3e0 [btrfs]
> ? cred_has_capability+0x7c/0x120
> ? legacy_get_tree+0x27/0x40
> legacy_get_tree+0x27/0x40
> vfs_get_tree+0x25/0xb0
> do_mount+0x735/0xa40
> __x64_sys_mount+0x8e/0xd0
> do_syscall_64+0x4d/0x90
> entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x7f5302f851be
>
> Fixes: b8522a1e5f42 ("btrfs: Factor out tree roots initialization during mount")
> Reported-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Added to misc-next with Niks explanation, thanks.
