Описание
In the Linux kernel, the following vulnerability has been resolved:
net: skbuff: add overflow debug check to pull/push helpers
syzbot managed to trigger following splat: BUG: KASAN: use-after-free in __skb_flow_dissect+0x4a3b/0x5e50 Read of size 1 at addr ffff888208a4000e by task a.out/2313 [..] __skb_flow_dissect+0x4a3b/0x5e50 __skb_get_hash+0xb4/0x400 ip_tunnel_xmit+0x77e/0x26f0 ipip_tunnel_xmit+0x298/0x410 ..
Analysis shows that the skb has a valid ->head, but bogus ->data pointer.
skb->data gets its bogus value via the neigh layer, which does:
1556 __skb_pull(skb, skb_network_offset(skb));
... and the skb was already dodgy at this point:
skb_network_offset(skb) returns a negative value due to an earlier overflow of skb->network_header (u16). __skb_pull thus "adjusts" skb->data by a huge offset, pointing outside skb->head area.
Allow debug builds to splat when we try to pull/push more than INT_MAX bytes.
After this, the syzkaller reproducer yields a more pr...
In the Linux kernel, the following vulnerability has been resolved:
net: skbuff: add overflow debug check to pull/push helpers
syzbot managed to trigger following splat: BUG: KASAN: use-after-free in __skb_flow_dissect+0x4a3b/0x5e50 Read of size 1 at addr ffff888208a4000e by task a.out/2313 [..] __skb_flow_dissect+0x4a3b/0x5e50 __skb_get_hash+0xb4/0x400 ip_tunnel_xmit+0x77e/0x26f0 ipip_tunnel_xmit+0x298/0x410 ..
Analysis shows that the skb has a valid ->head, but bogus ->data pointer.
skb->data gets its bogus value via the neigh layer, which does:
1556 __skb_pull(skb, skb_network_offset(skb));
... and the skb was already dodgy at this point:
skb_network_offset(skb) returns a negative value due to an earlier overflow of skb->network_header (u16). __skb_pull thus "adjusts" skb->data by a huge offset, pointing outside skb->head area.
Allow debug builds to splat when we try to pull/push more than INT_MAX bytes.
After this, the syzkaller reproducer yields a more precise splat before the flow dissector attempts to read off skb->data memory:
WARNING: CPU: 5 PID: 2313 at include/linux/skbuff.h:2653 neigh_connected_output+0x28e/0x400 ip_finish_output2+0xb25/0xed0 iptunnel_xmit+0x4ff/0x870 ipgre_xmit+0x78e/0xbb0
Ссылки
- https://nvd.nist.gov/vuln/detail/CVE-2024-35941
- https://git.kernel.org/stable/c/1b2b26595bb09febf14c5444c873ac4ec90a5a77
- https://git.kernel.org/stable/c/219eee9c0d16f1b754a8b85275854ab17df0850a
- https://git.kernel.org/stable/c/8af60bb2b215f478b886f1d6d302fefa7f0b917d
- https://git.kernel.org/stable/c/fff05b2b004d9a8a2416d08647f3dc9068e357c8
CVE ID
Связанные уязвимости
Rejected reason: This CVE ID has been rejected or withdrawn by its CVE Numbering Authority.
[REJECTED CVE] A use-after-free vulnerability was identified in the Linux kernel's net subsystem, specifically in skbuff handling. The issue arises from an overflow of the skb->network_header (a u16 value), causing skb_network_offset(skb) to return a negative value. This results in the __skb_pull() function incorrectly adjusting skb->data to an invalid memory location outside the skb->head area. An attacker could exploit this flaw to cause memory corruption or crash the system, potentially leading to denial of service or other undefined behavior.
Rejected reason: This CVE ID has been rejected or withdrawn by its CVE Numbering Authority.