CVE-2021-47256
- Source
- https://cve.org/CVERecord?id=CVE-2021-47256
- Import Source
- https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-47256.json
- JSON Data
- https://api.osv.dev/v1/vulns/CVE-2021-47256
- Downstream
- Published
- 2024-05-21T15:15:14Z
- Modified
- 2026-03-15T22:43:09Z
- Severity
-
- 5.5 (Medium) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
- Summary
- [none]
- Details
-
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.
- References
-
- https://git.kernel.org/stable/c/566345aaabac853aa866f53a219c4b02a6beb527
- https://git.kernel.org/stable/c/6d210d547adc2218ef8b5bcf23518c5f2f1fd872
- https://git.kernel.org/stable/c/9e379da727a7a031be9b877cde7b9c34a0fb8306
- https://git.kernel.org/stable/c/d05267fd27a5c4f54e06daefa3035995d765ca0c
- https://git.kernel.org/stable/c/e8675d291ac007e1c636870db880f837a9ea112a
- https://git.kernel.org/stable/c/28788dc5c70597395b6b451dae4549bbaa8e2c56
Affected packages
Git /
Database specific
source
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-47256.json"
unresolved_ranges
[
{
"events": [
{
"introduced": "3.16"
},
{
"fixed": "4.14.238"
}
]
},
{
"events": [
{
"introduced": "4.15"
},
{
"fixed": "4.19.196"
}
]
},
{
"events": [
{
"introduced": "4.20"
},
{
"fixed": "5.4.128"
}
]
},
{
"events": [
{
"introduced": "5.5"
},
{
"fixed": "5.10.46"
}
]
},
{
"events": [
{
"introduced": "5.11"
},
{
"fixed": "5.12.13"
}
]
},
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "5.13-rc1"
}
]
},
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "5.13-rc2"
}
]
},
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "5.13-rc3"
}
]
},
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "5.13-rc4"
}
]
},
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "5.13-rc5"
}
]
},
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "5.13-rc6"
}
]
}
]