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814a81c842
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.
Fixes:
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|---|---|---|
| .. | ||
| 6lowpan | ||
| 9p | ||
| 802 | ||
| 8021q | ||
| atm | ||
| batman-adv | ||
| bluetooth | ||
| bpf | ||
| bridge | ||
| can | ||
| ceph | ||
| core | ||
| dcb | ||
| devlink | ||
| dns_resolver | ||
| dsa | ||
| ethernet | ||
| ethtool | ||
| handshake | ||
| hsr | ||
| ieee802154 | ||
| ife | ||
| ipv4 | ||
| ipv6 | ||
| iucv | ||
| kcm | ||
| key | ||
| l2tp | ||
| l3mdev | ||
| lapb | ||
| llc | ||
| mac80211 | ||
| mac802154 | ||
| mctp | ||
| mpls | ||
| mptcp | ||
| ncsi | ||
| netfilter | ||
| netlabel | ||
| netlink | ||
| nfc | ||
| nsh | ||
| openvswitch | ||
| packet | ||
| phonet | ||
| psample | ||
| psp | ||
| qrtr | ||
| rds | ||
| rfkill | ||
| rxrpc | ||
| sched | ||
| sctp | ||
| shaper | ||
| smc | ||
| strparser | ||
| sunrpc | ||
| switchdev | ||
| tipc | ||
| tls | ||
| unix | ||
| vmw_vsock | ||
| wireless | ||
| x25 | ||
| xdp | ||
| xfrm | ||
| compat.c | ||
| devres.c | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||
| socket.c | ||
| sysctl_net.c | ||