CVE-2022-48847 Information

Description

In the Linux kernel the following vulnerability has been resolved:

watch_queue: Fix filter limit check

In watch_queue_set_filter() there are a couple of places where we check that the filter type value does not exceed what the type_filter bitmap can hold. One place calculates the number of bits by:

if (tf[i].type >= sizeof(wfilter->type_filter) 8)

which is fine but the second does:

if (tf[i].type >= sizeof(wfilter->type_filter) BITS_PER_LONG)

which is not. This can lead to a couple of out-of-bounds writes due to a too-large type:

(1) __set_bit() on wfilter->type_filter (2) Writing more elements in wfilter->filters[] than we allocated.

Fix this by just using the proper WATCH_TYPE__NR instead which is the number of types we actually know about.

The bug may cause an oops looking something like:

BUG: KASAN: slab-out-of-bounds in watch_queue_set_filter+0x659/0x740 Write of size 4 at addr ffff88800d2c66bc by task watch_queue_oob/611 … Call Trace: dump_stack_lvl+0x45/0x59 print_address_description.constprop.0+0x1f/0x150 … kasan_report.cold+0x7f/0x11b … watch_queue_set_filter+0x659/0x740 … __x64_sys_ioctl+0x127/0x190 do_syscall_64+0x43/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae

Allocated by task 611: kasan_save_stack+0x1e/0x40 __kasan_kmalloc+0x81/0xa0 watch_queue_set_filter+0x23a/0x740 __x64_sys_ioctl+0x127/0x190 do_syscall_64+0x43/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff88800d2c66a0 which belongs to the cache kmalloc-32 of size 32 The buggy address is located 28 bytes inside of 32-byte region [ffff88800d2c66a0 ffff88800d2c66c0)

Reference

https://git.kernel.org/stable/c/648895da69ced90ca770fd941c3d9479a9d72c16 https://git.kernel.org/stable/c/1b09f28f70a5046acd64138075ae3f095238b045 https://git.kernel.org/stable/c/b36588ebbcef74583824c08352e75838d6fb4ff2 https://git.kernel.org/stable/c/c993ee0f9f81caf5767a50d1faeba39a0dc82af2