CVE-2024-26611

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

xsk: fix usage of multi-buffer BPF helpers for ZC XDP

Currently when packet is shrunk via bpfxdpadjusttail() and memory type is set to MEMTYPEXSKBUFF_POOL, null ptr dereference happens:

[1136314.192256] BUG: kernel NULL pointer dereference, address: 0000000000000034 [1136314.203943] #PF: supervisor read access in kernel mode [1136314.213768] #PF: errorcode(0x0000) - not-present page [1136314.223550] PGD 0 P4D 0 [1136314.230684] Oops: 0000 [#1] PREEMPT SMP NOPTI [1136314.239621] CPU: 8 PID: 54203 Comm: xdpsock Not tainted 6.6.0+ #257 [1136314.250469] Hardware name: Intel Corporation S2600WFT/S2600WFT, BIOS SE5C620.86B.02.01.0008.031920191559 03/19/2019 [1136314.265615] RIP: 0010:xdpreturn+0x6c/0x210 [1136314.274653] Code: ad 00 48 8b 47 08 49 89 f8 a8 01 0f 85 9b 01 00 00 0f 1f 44 00 00 f0 41 ff 48 34 75 32 4c 89 c7 e9 79 cd 80 ff 83 fe 03 75 17 <f6> 41 34 01 0f 85 02 01 00 00 48 89 cf e9 22 cc 1e 00 e9 3d d2 86 [1136314.302907] RSP: 0018:ffffc900089f8db0 EFLAGS: 00010246 [1136314.312967] RAX: ffffc9003168aed0 RBX: ffff8881c3300000 RCX: 0000000000000000 [1136314.324953] RDX: 0000000000000000 RSI: 0000000000000003 RDI: ffffc9003168c000 [1136314.336929] RBP: 0000000000000ae0 R08: 0000000000000002 R09: 0000000000010000 [1136314.348844] R10: ffffc9000e495000 R11: 0000000000000040 R12: 0000000000000001 [1136314.360706] R13: 0000000000000524 R14: ffffc9003168aec0 R15: 0000000000000001 [1136314.373298] FS: 00007f8df8bbcb80(0000) GS:ffff8897e0e00000(0000) knlGS:0000000000000000 [1136314.386105] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [1136314.396532] CR2: 0000000000000034 CR3: 00000001aa912002 CR4: 00000000007706f0 [1136314.408377] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [1136314.420173] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [1136314.431890] PKRU: 55555554 [1136314.439143] Call Trace: [1136314.446058] <IRQ> [1136314.452465] ? _die+0x20/0x70 [1136314.459881] ? pagefaultoops+0x15b/0x440 [1136314.468305] ? excpagefault+0x6a/0x150 [1136314.476491] ? asmexcpagefault+0x22/0x30 [1136314.484927] ? _xdpreturn+0x6c/0x210 [1136314.492863] bpfxdpadjusttail+0x155/0x1d0 [1136314.501269] bpfprogccc47ae29d3b6570xdpsockprog+0x15/0x60 [1136314.511263] icecleanrxirqzc+0x206/0xc60 [ice] [1136314.520222] ? icexmitzc+0x6e/0x150 [ice] [1136314.528506] icenapipoll+0x467/0x670 [ice] [1136314.536858] ? ttwudoactivate.constprop.0+0x8f/0x1a0 [1136314.546010] _napipoll+0x29/0x1b0 [1136314.553462] netrxaction+0x133/0x270 [1136314.561619] _dosoftirq+0xbe/0x28e [1136314.569303] do_softirq+0x3f/0x60

This comes from _xdpreturn() call with xdpbuff argument passed as NULL which is supposed to be consumed by xskbuff_free() call.

To address this properly, in ZC case, a node that represents the frag being removed has to be pulled out of xskblist. Introduce appropriate xsk helpers to do such node operation and use them accordingly within bpfxdpadjusttail().