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vulnrichmentLinuxVULNRICHMENT:CVE-2021-47127
HistoryMar 15, 2024 - 8:14 p.m.

CVE-2021-47127 ice: track AF_XDP ZC enabled queues in bitmap

2024-03-1520:14:31
Linux
github.com
1
linux kernel
vulnerability resolved
af_xdp
copy mode
regression
null pointer
ice driver
xsk pool
xsk_buff_pool
bitmap
zero-copy
napi poll

AI Score

6.5

Confidence

Low

SSVC

Exploitation

none

Automatable

no

Technical Impact

partial

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

ice: track AF_XDP ZC enabled queues in bitmap

Commit c7a219048e45 (“ice: Remove xsk_buff_pool from VSI structure”)
silently introduced a regression and broke the Tx side of AF_XDP in copy
mode. xsk_pool on ice_ring is set only based on the existence of the XDP
prog on the VSI which in turn picks ice_clean_tx_irq_zc to be executed.
That is not something that should happen for copy mode as it should use
the regular data path ice_clean_tx_irq.

This results in a following splat when xdpsock is run in txonly or l2fwd
scenarios in copy mode:

<snip>
[ 106.050195] BUG: kernel NULL pointer dereference, address: 0000000000000030
[ 106.057269] #PF: supervisor read access in kernel mode
[ 106.062493] #PF: error_code(0x0000) - not-present page
[ 106.067709] PGD 0 P4D 0
[ 106.070293] Oops: 0000 [#1] PREEMPT SMP NOPTI
[ 106.074721] CPU: 61 PID: 0 Comm: swapper/61 Not tainted 5.12.0-rc2+ #45
[ 106.081436] Hardware name: Intel Corporation S2600WFT/S2600WFT, BIOS SE5C620.86B.02.01.0008.031920191559 03/19/2019
[ 106.092027] RIP: 0010:xp_raw_get_dma+0x36/0x50
[ 106.096551] Code: 74 14 48 b8 ff ff ff ff ff ff 00 00 48 21 f0 48 c1 ee 30 48 01 c6 48 8b 87 90 00 00 00 48 89 f2 81 e6 ff 0f 00 00 48 c1 ea 0c <48> 8b 04 d0 48 83 e0 fe 48 01 f0 c3 66 66 2e 0f 1f 84 00 00 00 00
[ 106.115588] RSP: 0018:ffffc9000d694e50 EFLAGS: 00010206
[ 106.120893] RAX: 0000000000000000 RBX: ffff88984b8c8a00 RCX: ffff889852581800
[ 106.128137] RDX: 0000000000000006 RSI: 0000000000000000 RDI: ffff88984cd8b800
[ 106.135383] RBP: ffff888123b50001 R08: ffff889896800000 R09: 0000000000000800
[ 106.142628] R10: 0000000000000000 R11: ffffffff826060c0 R12: 00000000000000ff
[ 106.149872] R13: 0000000000000000 R14: 0000000000000040 R15: ffff888123b50018
[ 106.157117] FS: 0000000000000000(0000) GS:ffff8897e0f40000(0000) knlGS:0000000000000000
[ 106.165332] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 106.171163] CR2: 0000000000000030 CR3: 000000000560a004 CR4: 00000000007706e0
[ 106.178408] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 106.185653] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 106.192898] PKRU: 55555554
[ 106.195653] Call Trace:
[ 106.198143] <IRQ>
[ 106.200196] ice_clean_tx_irq_zc+0x183/0x2a0 [ice]
[ 106.205087] ice_napi_poll+0x3e/0x590 [ice]
[ 106.209356] __napi_poll+0x2a/0x160
[ 106.212911] net_rx_action+0xd6/0x200
[ 106.216634] __do_softirq+0xbf/0x29b
[ 106.220274] irq_exit_rcu+0x88/0xc0
[ 106.223819] common_interrupt+0x7b/0xa0
[ 106.227719] </IRQ>
[ 106.229857] asm_common_interrupt+0x1e/0x40
</snip>

Fix this by introducing the bitmap of queues that are zero-copy enabled,
where each bit, corresponding to a queue id that xsk pool is being
configured on, will be set/cleared within ice_xsk_pool_{en,dis}able and
checked within ice_xsk_pool(). The latter is a function used for
deciding which napi poll routine is executed.
Idea is being taken from our other drivers such as i40e and ixgbe.

AI Score

6.5

Confidence

Low

SSVC

Exploitation

none

Automatable

no

Technical Impact

partial

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