scsi: hisi_sas: Grab sas_dev lock when traversing the members of sas_dev.list
CVE: CVE-2023-53627
Component: kernel
CWE: CWE-820
Severity: Moderate
CVSS v3: 6.7/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
Release date: 2023-01-01T00:00:00+00:00

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

scsi: hisi_sas: Grab sas_dev lock when traversing the members of sas_dev.list

When freeing slots in function slot_complete_v3_hw(), it is possible that
sas_dev.list is being traversed elsewhere, and it may trigger a NULL
pointer exception, such as follows:

==>cq thread                    ==>scsi_eh_6

                                ==>scsi_error_handler()
				  ==>sas_eh_handle_sas_errors()
				    ==>sas_scsi_find_task()
				      ==>lldd_abort_task()
==>slot_complete_v3_hw()              ==>hisi_sas_abort_task()
  ==>hisi_sas_slot_task_free()	        ==>dereg_device_v3_hw()
    ==>list_del_init()        		  ==>list_for_each_entry_safe()

[ 7165.434918] sas: Enter sas_scsi_recover_host busy: 32 failed: 32
[ 7165.434926] sas: trying to find task 0x00000000769b5ba5
[ 7165.434927] sas: sas_scsi_find_task: aborting task 0x00000000769b5ba5
[ 7165.434940] hisi_sas_v3_hw 0000:b4:02.0: slot complete: task(00000000769b5ba5) aborted
[ 7165.434964] hisi_sas_v3_hw 0000:b4:02.0: slot complete: task(00000000c9f7aa07) ignored
[ 7165.434965] hisi_sas_v3_hw 0000:b4:02.0: slot complete: task(00000000e2a1cf01) ignored
[ 7165.434968] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[ 7165.434972] hisi_sas_v3_hw 0000:b4:02.0: slot complete: task(0000000022d52d93) ignored
[ 7165.434975] hisi_sas_v3_hw 0000:b4:02.0: slot complete: task(0000000066a7516c) ignored
[ 7165.434976] Mem abort info:
[ 7165.434982]   ESR = 0x96000004
[ 7165.434991]   Exception class = DABT (current EL), IL = 32 bits
[ 7165.434992]   SET = 0, FnV = 0
[ 7165.434993]   EA = 0, S1PTW = 0
[ 7165.434994] Data abort info:
[ 7165.434994]   ISV = 0, ISS = 0x00000004
[ 7165.434995]   CM = 0, WnR = 0
[ 7165.434997] user pgtable: 4k pages, 48-bit VAs, pgdp = 00000000f29543f2
[ 7165.434998] [0000000000000000] pgd=0000000000000000
[ 7165.435003] Internal error: Oops: 96000004 [#1] SMP
[ 7165.439863] Process scsi_eh_6 (pid: 4109, stack limit = 0x00000000c43818d5)
[ 7165.468862] pstate: 00c00009 (nzcv daif +PAN +UAO)
[ 7165.473637] pc : dereg_device_v3_hw+0x68/0xa8 [hisi_sas_v3_hw]
[ 7165.479443] lr : dereg_device_v3_hw+0x2c/0xa8 [hisi_sas_v3_hw]
[ 7165.485247] sp : ffff00001d623bc0
[ 7165.488546] x29: ffff00001d623bc0 x28: ffffa027d03b9508
[ 7165.493835] x27: ffff80278ed50af0 x26: ffffa027dd31e0a8
[ 7165.499123] x25: ffffa027d9b27f88 x24: ffffa027d9b209f8
[ 7165.504411] x23: ffffa027c45b0d60 x22: ffff80278ec07c00
[ 7165.509700] x21: 0000000000000008 x20: ffffa027d9b209f8
[ 7165.514988] x19: ffffa027d9b27f88 x18: ffffffffffffffff
[ 7165.520276] x17: 0000000000000000 x16: 0000000000000000
[ 7165.525564] x15: ffff0000091d9708 x14: ffff0000093b7dc8
[ 7165.530852] x13: ffff0000093b7a23 x12: 6e7265746e692067
[ 7165.536140] x11: 0000000000000000 x10: 0000000000000bb0
[ 7165.541429] x9 : ffff00001d6238f0 x8 : ffffa027d877af00
[ 7165.546718] x7 : ffffa027d6329600 x6 : ffff7e809f58ca00
[ 7165.552006] x5 : 0000000000001f8a x4 : 000000000000088e
[ 7165.557295] x3 : ffffa027d9b27fa8 x2 : 0000000000000000
[ 7165.562583] x1 : 0000000000000000 x0 : 000000003000188e
[ 7165.567872] Call trace:
[ 7165.570309]  dereg_device_v3_hw+0x68/0xa8 [hisi_sas_v3_hw]
[ 7165.575775]  hisi_sas_abort_task+0x248/0x358 [hisi_sas_main]
[ 7165.581415]  sas_eh_handle_sas_errors+0x258/0x8e0 [libsas]
[ 7165.586876]  sas_scsi_recover_host+0x134/0x458 [libsas]
[ 7165.592082]  scsi_error_handler+0xb4/0x488
[ 7165.596163]  kthread+0x134/0x138
[ 7165.599380]  ret_from_fork+0x10/0x18
[ 7165.602940] Code: d5033e9f b9000040 aa0103e2 eb03003f (f9400021)
[ 7165.609004] kernel fault(0x1) notification starting on CPU 75
[ 7165.700728] ---[ end trace fc042cbbea224efc ]---
[ 7165.705326] Kernel panic - not syncing: Fatal exception

To fix the issue, grab sas_dev lock when traversing the members of
sas_dev.list in dereg_device_v3_hw() and hisi_sas_release_tasks() to avoid
concurrency of adding and deleting member. When 
---truncated---

Statement: The issue arises because of missing locking when accessing the shared sas_dev.list structure. Two code paths can execute concurrently: the completion queue thread (cq thread) calls slot_complete_v3_hw() → hisi_sas_slot_task_free() → list_del_init() to remove completed task slots, while the SCSI error handler thread calls sas_scsi_find_task() → hisi_sas_abort_task() → dereg_device_v3_hw() → list_for_each_entry_safe() to traverse the same list when aborting tasks. Without synchronization, the deletion can invalidate list pointers while traversal is in progress. When the error handler attempts to follow the next pointer in the list after a concurrent deletion, it dereferences a NULL or freed pointer (register x1 = 0x0000000000000000 in the crash dump), causing a kernel panic. The race window is narrow and requires precise timing between I/O completion and error handling paths, which can be triggered under heavy I/O workload with concurrent errors. While this reliably causes availability impact through kernel panics, the underlying list corruption represents a memory safety violation. With sufficient control over timing and heap layout, race conditions on linked list structures can potentially be leveraged for more sophisticated attacks beyond denial of service, though such exploitation would be complex.

Remediation:
To mitigate this issue, prevent the hisi_sas_v3_hw module from loading. See https://access.redhat.com/solutions/41278 for instructions on blacklisting kernel modules.