CVE-2022-48919 in Linux
Summary
by MITRE • 08/22/2024
In the Linux kernel, the following vulnerability has been resolved:
cifs: fix double free race when mount fails in cifs_get_root()
When cifs_get_root() fails during cifs_smb3_do_mount() we call deactivate_locked_super() which eventually will call delayed_free() which will free the context. In this situation we should not proceed to enter the out: section in cifs_smb3_do_mount() and free the same resources a second time.
[Thu Feb 10 12:59:06 2022] BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x32/0x60
[Thu Feb 10 12:59:06 2022] Read of size 8 at addr ffff888364f4d110 by task swapper/1/0
[Thu Feb 10 12:59:06 2022] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G OE 5.17.0-rc3+ #4
[Thu Feb 10 12:59:06 2022] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.0 12/17/2019
[Thu Feb 10 12:59:06 2022] Call Trace:
[Thu Feb 10 12:59:06 2022] <IRQ>
[Thu Feb 10 12:59:06 2022] dump_stack_lvl+0x5d/0x78
[Thu Feb 10 12:59:06 2022] print_address_description.constprop.0+0x24/0x150
[Thu Feb 10 12:59:06 2022] ? rcu_cblist_dequeue+0x32/0x60
[Thu Feb 10 12:59:06 2022] kasan_report.cold+0x7d/0x117
[Thu Feb 10 12:59:06 2022] ? rcu_cblist_dequeue+0x32/0x60
[Thu Feb 10 12:59:06 2022] __asan_load8+0x86/0xa0
[Thu Feb 10 12:59:06 2022] rcu_cblist_dequeue+0x32/0x60
[Thu Feb 10 12:59:06 2022] rcu_core+0x547/0xca0
[Thu Feb 10 12:59:06 2022] ? call_rcu+0x3c0/0x3c0
[Thu Feb 10 12:59:06 2022] ? __this_cpu_preempt_check+0x13/0x20
[Thu Feb 10 12:59:06 2022] ? lock_is_held_type+0xea/0x140
[Thu Feb 10 12:59:06 2022] rcu_core_si+0xe/0x10
[Thu Feb 10 12:59:06 2022] __do_softirq+0x1d4/0x67b
[Thu Feb 10 12:59:06 2022] __irq_exit_rcu+0x100/0x150
[Thu Feb 10 12:59:06 2022] irq_exit_rcu+0xe/0x30
[Thu Feb 10 12:59:06 2022] sysvec_hyperv_stimer0+0x9d/0xc0
... [Thu Feb 10 12:59:07 2022] Freed by task 58179:
[Thu Feb 10 12:59:07 2022] kasan_save_stack+0x26/0x50
[Thu Feb 10 12:59:07 2022] kasan_set_track+0x25/0x30
[Thu Feb 10 12:59:07 2022] kasan_set_free_info+0x24/0x40
[Thu Feb 10 12:59:07 2022] ____kasan_slab_free+0x137/0x170
[Thu Feb 10 12:59:07 2022] __kasan_slab_free+0x12/0x20
[Thu Feb 10 12:59:07 2022] slab_free_freelist_hook+0xb3/0x1d0
[Thu Feb 10 12:59:07 2022] kfree+0xcd/0x520
[Thu Feb 10 12:59:07 2022] cifs_smb3_do_mount+0x149/0xbe0 [cifs]
[Thu Feb 10 12:59:07 2022] smb3_get_tree+0x1a0/0x2e0 [cifs]
[Thu Feb 10 12:59:07 2022] vfs_get_tree+0x52/0x140
[Thu Feb 10 12:59:07 2022] path_mount+0x635/0x10c0
[Thu Feb 10 12:59:07 2022] __x64_sys_mount+0x1bf/0x210
[Thu Feb 10 12:59:07 2022] do_syscall_64+0x5c/0xc0
[Thu Feb 10 12:59:07 2022] entry_SYSCALL_64_after_hwframe+0x44/0xae
[Thu Feb 10 12:59:07 2022] Last potentially related work creation:
[Thu Feb 10 12:59:07 2022] kasan_save_stack+0x26/0x50
[Thu Feb 10 12:59:07 2022] __kasan_record_aux_stack+0xb6/0xc0
[Thu Feb 10 12:59:07 2022] kasan_record_aux_stack_noalloc+0xb/0x10
[Thu Feb 10 12:59:07 2022] call_rcu+0x76/0x3c0
[Thu Feb 10 12:59:07 2022] cifs_umount+0xce/0xe0 [cifs]
[Thu Feb 10 12:59:07 2022] cifs_kill_sb+0xc8/0xe0 [cifs]
[Thu Feb 10 12:59:07 2022] deactivate_locked_super+0x5d/0xd0
[Thu Feb 10 12:59:07 2022] cifs_smb3_do_mount+0xab9/0xbe0 [cifs]
[Thu Feb 10 12:59:07 2022] smb3_get_tree+0x1a0/0x2e0 [cifs]
[Thu Feb 10 12:59:07 2022] vfs_get_tree+0x52/0x140
[Thu Feb 10 12:59:07 2022] path_mount+0x635/0x10c0
[Thu Feb 10 12:59:07 2022] __x64_sys_mount+0x1bf/0x210
[Thu Feb 10 12:59:07 2022] do_syscall_64+0x5c/0xc0
[Thu Feb 10 12:59:07 2022] entry_SYSCALL_64_after_hwframe+0x44/0xae
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Analysis
by VulDB Data Team • 12/23/2025
The vulnerability described in CVE-2022-48919 affects the Linux kernel's Common Internet File System (CIFS) implementation, specifically within the cifs_smb3_do_mount() function. This issue manifests as a double free race condition that occurs when a CIFS mount operation fails during the cifs_get_root() phase. The root cause stems from improper resource management logic where the system attempts to free memory resources twice, leading to a use-after-free error that can result in system instability or potential exploitation.
The technical flaw occurs when cifs_get_root() fails during the mounting process, triggering a call to deactivate_locked_super() which eventually invokes delayed_free() to release the context. However, the code flow does not properly prevent execution from continuing to the out: section in cifs_smb3_do_mount(), which attempts to free the same resources a second time. This creates a race condition where memory is freed once by delayed_free() and then again by the subsequent out: block, resulting in a use-after-free condition as evidenced by the KASAN report showing a read operation on freed memory address.
The operational impact of this vulnerability extends beyond simple system crashes, as it can enable attackers to exploit the memory corruption to achieve arbitrary code execution or denial of service conditions. The KASAN stack trace reveals that the error occurs during RCU (Read-Copy-Update) callback processing, indicating that the memory corruption affects kernel subsystems responsible for concurrent access control. The vulnerability is particularly concerning in virtualized environments where multiple concurrent mount operations might increase the likelihood of triggering the race condition, as demonstrated by the Hyper-V virtual machine environment in the stack trace.
This vulnerability aligns with CWE-415, which addresses double free conditions in memory management, and maps to ATT&CK technique T1059.001 for command and scripting interpreter, as successful exploitation could allow attackers to execute malicious code on the target system. The CIFS implementation's failure to properly handle error paths in mount operations creates a pathway for attackers to manipulate kernel memory structures through carefully crafted mount requests. Mitigation strategies should focus on ensuring proper resource management in error handling paths and implementing additional checks to prevent double-free scenarios in kernel modules. The fix requires modifying the cifs_smb3_do_mount() function to properly exit early when cifs_get_root() fails, preventing the redundant resource deallocation that leads to the memory corruption.