| From bippy-d175d3acf727 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2024-35941: net: skbuff: add overflow debug check to pull/push helpers |
| |
| Description |
| =========== |
| |
| 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 |
| |
| The Linux kernel CVE team has assigned CVE-2024-35941 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Fixed in 6.1.86 with commit 8af60bb2b215 |
| Fixed in 6.6.27 with commit 1b2b26595bb0 |
| Fixed in 6.8.6 with commit fff05b2b004d |
| Fixed in 6.9 with commit 219eee9c0d16 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2024-35941 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| include/linux/skbuff.h |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/8af60bb2b215f478b886f1d6d302fefa7f0b917d |
| https://git.kernel.org/stable/c/1b2b26595bb09febf14c5444c873ac4ec90a5a77 |
| https://git.kernel.org/stable/c/fff05b2b004d9a8a2416d08647f3dc9068e357c8 |
| https://git.kernel.org/stable/c/219eee9c0d16f1b754a8b85275854ab17df0850a |
