CVE-2021-47256: mm/memory-failure: make sure wait for page writeback in memory_failure
First published: Tue May 21 2024(Updated: )
In the Linux kernel, the following vulnerability has been resolved: mm/memory-failure: make sure wait for page writeback in memory_failure Our syzkaller trigger the "BUG_ON(!list_empty(&inode->i_wb_list))" in clear_inode: kernel BUG at fs/inode.c:519! Internal error: Oops - BUG: 0 [#1] SMP Modules linked in: Process syz-executor.0 (pid: 249, stack limit = 0x00000000a12409d7) CPU: 1 PID: 249 Comm: syz-executor.0 Not tainted 4.19.95 Hardware name: linux,dummy-virt (DT) pstate: 80000005 (Nzcv daif -PAN -UAO) pc : clear_inode+0x280/0x2a8 lr : clear_inode+0x280/0x2a8 Call trace: clear_inode+0x280/0x2a8 ext4_clear_inode+0x38/0xe8 ext4_free_inode+0x130/0xc68 ext4_evict_inode+0xb20/0xcb8 evict+0x1a8/0x3c0 iput+0x344/0x460 do_unlinkat+0x260/0x410 __arm64_sys_unlinkat+0x6c/0xc0 el0_svc_common+0xdc/0x3b0 el0_svc_handler+0xf8/0x160 el0_svc+0x10/0x218 Kernel panic - not syncing: Fatal exception A crash dump of this problem show that someone called __munlock_pagevec to clear page LRU without lock_page: do_mmap -> mmap_region -> do_munmap -> munlock_vma_pages_range -> __munlock_pagevec. As a result memory_failure will call identify_page_state without wait_on_page_writeback. And after truncate_error_page clear the mapping of this page. end_page_writeback won't call sb_clear_inode_writeback to clear inode->i_wb_list. That will trigger BUG_ON in clear_inode! Fix it by checking PageWriteback too to help determine should we skip wait_on_page_writeback.
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Red Hat Kernel-devel | ||
| Linux Kernel | >=3.16<4.14.238 | |
| Linux Kernel | >=4.15<4.19.196 | |
| Linux Kernel | >=4.20<5.4.128 | |
| Linux Kernel | >=5.5<5.10.46 | |
| Linux Kernel | >=5.11<5.12.13 | |
| Linux Kernel | =5.13-rc1 | |
| Linux Kernel | =5.13-rc2 | |
| Linux Kernel | =5.13-rc3 | |
| Linux Kernel | =5.13-rc4 | |
| Linux Kernel | =5.13-rc5 | |
| Linux Kernel | =5.13-rc6 |
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Reference Links
- https://git.kernel.org/stable/c/d05267fd27a5c4f54e06daefa3035995d765ca0c
- https://git.kernel.org/stable/c/6d210d547adc2218ef8b5bcf23518c5f2f1fd872
- https://git.kernel.org/stable/c/566345aaabac853aa866f53a219c4b02a6beb527
- https://git.kernel.org/stable/c/9e379da727a7a031be9b877cde7b9c34a0fb8306
- https://git.kernel.org/stable/c/28788dc5c70597395b6b451dae4549bbaa8e2c56
- https://git.kernel.org/stable/c/e8675d291ac007e1c636870db880f837a9ea112a
Frequently Asked Questions
What is the severity of CVE-2021-47256?
CVE-2021-47256 has a severity rating that depends on the specific Linux kernel version in use and its configuration.
How do I fix CVE-2021-47256?
To fix CVE-2021-47256, update your Linux kernel to the latest patched version as provided by your distribution vendor.
What are the potential impacts of CVE-2021-47256?
CVE-2021-47256 may lead to system crashes or unexpected behavior when handling memory faults.
Which Linux kernel versions are affected by CVE-2021-47256?
CVE-2021-47256 affects specific versions of the Linux kernel, so refer to your distribution's advisories for details.
Is there an exploit available for CVE-2021-47256?
While CVE-2021-47256 has been reported, the presence of an exploit would depend on the specific system setup and circumstances.
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