CVE-2021-47302

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

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

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