Subject: CVE-2021-47302: igc: Fix use-after-free error during reset

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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

igc: Fix use-after-free error during reset

Cleans the next descriptor to watch (next_to_watch) when cleaning the
TX ring.

Failure to do so can cause invalid memory accesses. If igc_poll() runs
while the controller is being reset this can lead to the driver try to
free a skb that was already freed.

Log message:

 [  101.525242] refcount_t: underflow; use-after-free.
 [  101.525251] WARNING: CPU: 1 PID: 646 at lib/refcount.c:28 refcount_warn_saturate+0xab/0xf0
 [  101.525259] Modules linked in: sch_etf(E) sch_mqprio(E) rfkill(E) intel_rapl_msr(E) intel_rapl_common(E)
 x86_pkg_temp_thermal(E) intel_powerclamp(E) coretemp(E) binfmt_misc(E) kvm_intel(E) kvm(E) irqbypass(E) crc32_pclmul(E)
 ghash_clmulni_intel(E) aesni_intel(E) mei_wdt(E) libaes(E) crypto_simd(E) cryptd(E) glue_helper(E) snd_hda_codec_hdmi(E)
 rapl(E) intel_cstate(E) snd_hda_intel(E) snd_intel_dspcfg(E) sg(E) soundwire_intel(E) intel_uncore(E) at24(E)
 soundwire_generic_allocation(E) iTCO_wdt(E) soundwire_cadence(E) intel_pmc_bxt(E) serio_raw(E) snd_hda_codec(E)
 iTCO_vendor_support(E) watchdog(E) snd_hda_core(E) snd_hwdep(E) snd_soc_core(E) snd_compress(E) snd_pcsp(E)
 soundwire_bus(E) snd_pcm(E) evdev(E) snd_timer(E) mei_me(E) snd(E) soundcore(E) mei(E) configfs(E) ip_tables(E) x_tables(E)
 autofs4(E) ext4(E) crc32c_generic(E) crc16(E) mbcache(E) jbd2(E) sd_mod(E) t10_pi(E) crc_t10dif(E) crct10dif_generic(E)
 i915(E) ahci(E) libahci(E) ehci_pci(E) igb(E) xhci_pci(E) ehci_hcd(E)
 [  101.525303]  drm_kms_helper(E) dca(E) xhci_hcd(E) libata(E) crct10dif_pclmul(E) cec(E) crct10dif_common(E) tsn(E) igc(E)
 e1000e(E) ptp(E) i2c_i801(E) crc32c_intel(E) psmouse(E) i2c_algo_bit(E) i2c_smbus(E) scsi_mod(E) lpc_ich(E) pps_core(E)
 usbcore(E) drm(E) button(E) video(E)
 [  101.525318] CPU: 1 PID: 646 Comm: irq/37-enp7s0-T Tainted: G            E     5.10.30-rt37-tsn1-rt-ipipe #ipipe
 [  101.525320] Hardware name: SIEMENS AG SIMATIC IPC427D/A5E31233588, BIOS V17.02.09 03/31/2017
 [  101.525322] RIP: 0010:refcount_warn_saturate+0xab/0xf0
 [  101.525325] Code: 05 31 48 44 01 01 e8 f0 c6 42 00 0f 0b c3 80 3d 1f 48 44 01 00 75 90 48 c7 c7 78 a8 f3 a6 c6 05 0f 48
 44 01 01 e8 d1 c6 42 00 <0f> 0b c3 80 3d fe 47 44 01 00 0f 85 6d ff ff ff 48 c7 c7 d0 a8 f3
 [  101.525327] RSP: 0018:ffffbdedc0917cb8 EFLAGS: 00010286
 [  101.525329] RAX: 0000000000000000 RBX: ffff98fd6becbf40 RCX: 0000000000000001
 [  101.525330] RDX: 0000000000000001 RSI: ffffffffa6f2700c RDI: 00000000ffffffff
 [  101.525332] RBP: ffff98fd6becc14c R08: ffffffffa7463d00 R09: ffffbdedc0917c50
 [  101.525333] R10: ffffffffa74c3578 R11: 0000000000000034 R12: 00000000ffffff00
 [  101.525335] R13: ffff98fd6b0b1000 R14: 0000000000000039 R15: ffff98fd6be35c40
 [  101.525337] FS:  0000000000000000(0000) GS:ffff98fd6e240000(0000) knlGS:0000000000000000
 [  101.525339] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 [  101.525341] CR2: 00007f34135a3a70 CR3: 0000000150210003 CR4: 00000000001706e0
 [  101.525343] Call Trace:
 [  101.525346]  sock_wfree+0x9c/0xa0
 [  101.525353]  unix_destruct_scm+0x7b/0xa0
 [  101.525358]  skb_release_head_state+0x40/0x90
 [  101.525362]  skb_release_all+0xe/0x30
 [  101.525364]  napi_consume_skb+0x57/0x160
 [  101.525367]  igc_poll+0xb7/0xc80 [igc]
 [  101.525376]  ? sched_clock+0x5/0x10
 [  101.525381]  ? sched_clock_cpu+0xe/0x100
 [  101.525385]  net_rx_action+0x14c/0x410
 [  101.525388]  __do_softirq+0xe9/0x2f4
 [  101.525391]  __local_bh_enable_ip+0xe3/0x110
 [  101.525395]  ? irq_finalize_oneshot.part.47+0xe0/0xe0
 [  101.525398]  irq_forced_thread_fn+0x6a/0x80
 [  101.525401]  irq_thread+0xe8/0x180
 [  101.525403]  ? wake_threads_waitq+0x30/0x30
 [  101.525406]  ? irq_thread_check_affinity+0xd0/0xd0
 [  101.525408]  kthread+0x183/0x1a0
 [  101.525412]  ? kthread_park+0x80/0x80
 [  101.525415]  ret_from_fork+0x22/0x30

The Linux kernel CVE team has assigned CVE-2021-47302 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 4.20 with commit 13b5b7fd6a4a and fixed in 5.4.136 with commit a9508e0edfe3
	Issue introduced in 4.20 with commit 13b5b7fd6a4a and fixed in 5.10.54 with commit e15f629036ba
	Issue introduced in 4.20 with commit 13b5b7fd6a4a and fixed in 5.13.6 with commit ea5e36b7367e
	Issue introduced in 4.20 with commit 13b5b7fd6a4a and fixed in 5.14 with commit 56ea7ed103b4

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-2021-47302
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:
	drivers/net/ethernet/intel/igc/igc_main.c

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/a9508e0edfe369ac95d0825bcdca976436ce780f
	https://git.kernel.org/stable/c/e15f629036bac005fc758b4ad17896cf2312add4
	https://git.kernel.org/stable/c/ea5e36b7367ea0a36ef73a163768f16d2977bd83
	https://git.kernel.org/stable/c/56ea7ed103b46970e171eb1c95916f393d64eeff