CVE-2026-98588

In the Linux kernel, the following vulnerability has been resolved:

bpf, sockmap: Reject max_entries > INT_MAX in sock_map_alloc

sock_map_alloc() only rejects max_entries == 0 and otherwise allows any

u32 value. sock_map_free() then walks the sks[] array with a signed int

iterator:

int i;

for (i = 0; i < stab->map.max_entries; i++)

struct sock **psk = &stab->sks[i];

When a SOCKMAP is created with max_entries = 0xffffffff (UINT_MAX), the

allocation of 32 GiB can succeed on large-memory hosts. During free the

counter reaches 0x80000000, wraps to INT_MIN, is sign-extended by movslq

and turned into a ~16 GiB negative offset from stab->sks, pointing far

below the allocation.

The faulting access is an xchg() write in sock_map_free(). Without

KASAN, the same out-of-bounds write can fault on an unmapped vmalloc page

or corrupt an unrelated allocation if that vmalloc address is populated.

On a KASAN kernel with CONFIG_KASAN_VMALLOC=y, the shadow check for that

address hits an unmapped shadow page and oopses first:

BUG: unable to handle page fault for address: fffff521b59c5a00

RIP: 0010:kasan_check_range+0x107/0x190

Call Trace:

sock_map_free+0x93/0x190

map_create+0x68d/0xb30

__sys_bpf+0x21e/0x2e70

Vmcore confirmed stab->map.max_entries == 0xffffffff, stab->sks ==

0xffffc911ace2d000, and the faulting address sks + (s64)INT_MIN * 8

exactly at 0xffffc90dace2d000. The same buggy path is reached on the

normal close()/bpf_map_free_deferred() path whenever such a map is

destroyed.

sock_map_alloc() used to bound its allocation size through

bpf_map_charge_init(), but the bound was dropped when rlimit-based memory

accounting was removed. Reject max_entries > INT_MAX at creation time so

the signed iterator in sock_map_free() never sees a value that would

overflow.

Triggered by syzkaller and reproduced on both a 6.6-based KASAN kernel

and the upstream v7.3-rc2 kernel.