Hi, there is a slab-out-bounds Read bug in
__htab_map_lookup_and_delete_batch in kernel/bpf/hashtab.c
and I reproduce it in linux-5.16.rc7(upstream) and latest linux-5.15.11.
#carsh log
[ 166.945208][ T6897]
==================================================================
[ 166.947075][ T6897] BUG: KASAN: slab-out-of-bounds in _copy_to_user+0x87/0xb0
[ 166.948612][ T6897] Read of size 49 at addr ffff88801913f800 by
task __htab_map_look/6897
[ 166.950406][ T6897]
[ 166.950890][ T6897] CPU: 1 PID: 6897 Comm: __htab_map_look Not
tainted 5.16.0-rc7+ #30
[ 166.952521][ T6897] Hardware name: QEMU Standard PC (i440FX + PIIX,
1996), BIOS 1.13.0-1ubuntu1 04/01/2014
[ 166.954562][ T6897] Call Trace:
[ 166.955268][ T6897] <TASK>
[ 166.955918][ T6897] dump_stack_lvl+0x57/0x7d
[ 166.956875][ T6897] print_address_description.constprop.0.cold+0x93/0x347
[ 166.958411][ T6897] ? _copy_to_user+0x87/0xb0
[ 166.959356][ T6897] ? _copy_to_user+0x87/0xb0
[ 166.960272][ T6897] kasan_report.cold+0x83/0xdf
[ 166.961196][ T6897] ? _copy_to_user+0x87/0xb0
[ 166.962053][ T6897] kasan_check_range+0x13b/0x190
[ 166.962978][ T6897] _copy_to_user+0x87/0xb0
[ 166.964340][ T6897] __htab_map_lookup_and_delete_batch+0xdc2/0x1590
[ 166.965619][ T6897] ? htab_lru_map_update_elem+0xe70/0xe70
[ 166.966732][ T6897] bpf_map_do_batch+0x1fa/0x460
[ 166.967619][ T6897] __sys_bpf+0x99a/0x3860
[ 166.968443][ T6897] ? bpf_link_get_from_fd+0xd0/0xd0
[ 166.969393][ T6897] ? rcu_read_lock_sched_held+0x9c/0xd0
[ 166.970425][ T6897] ? lock_acquire+0x1ab/0x520
[ 166.971284][ T6897] ? find_held_lock+0x2d/0x110
[ 166.972208][ T6897] ? rcu_read_lock_sched_held+0x9c/0xd0
[ 166.973139][ T6897] ? rcu_read_lock_bh_held+0xb0/0xb0
[ 166.974096][ T6897] __x64_sys_bpf+0x70/0xb0
[ 166.974903][ T6897] ? syscall_enter_from_user_mode+0x21/0x70
[ 166.976077][ T6897] do_syscall_64+0x35/0xb0
[ 166.976889][ T6897] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 166.978027][ T6897] RIP: 0033:0x450f0d
In hashtable, if the elements' keys have the same jhash() value, the
elements will be put into the same bucket.
By putting a lot of elements into a single bucket, the value of
bucket_size can be increased to overflow.
but also we can increase bucket_cnt to out of bound Read.
the out of bound Read in __htab_map_lookup_and_delete_batch code:
```
...
if (bucket_cnt && (copy_to_user(ukeys + total * key_size, keys,
key_size * bucket_cnt) ||
copy_to_user(uvalues + total * value_size, values,
value_size * bucket_cnt))) {
ret = -EFAULT;
goto after_loop;
}
...
```
Regards,
butt3rflyh4ck.
--
Active Defense Lab of Venustech
