CVE-2021-47089 Affecting kernel-docs package, versions <5.14.21-150500.55.73.2
Threat Intelligence
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Test your applications- Snyk IDSNYK-SLES155-KERNELDOCS-7694463
- published17 Aug 2024
- disclosed16 Aug 2024
Introduced: 16 Aug 2024
CVE-2021-47089 (opens in a new tab)How to fix?
Upgrade SLES:15.5 kernel-docs to version 5.14.21-150500.55.73.2 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-docs package and not the kernel-docs package as distributed by SLES.
See How to fix? for SLES:15.5 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
kfence: fix memory leak when cat kfence objects
Hulk robot reported a kmemleak problem:
unreferenced object 0xffff93d1d8cc02e8 (size 248):
comm "cat", pid 23327, jiffies 4624670141 (age 495992.217s)
hex dump (first 32 bytes):
00 40 85 19 d4 93 ff ff 00 10 00 00 00 00 00 00 .@..............
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
seq_open+0x2a/0x80
full_proxy_open+0x167/0x1e0
do_dentry_open+0x1e1/0x3a0
path_openat+0x961/0xa20
do_filp_open+0xae/0x120
do_sys_openat2+0x216/0x2f0
do_sys_open+0x57/0x80
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xa9
unreferenced object 0xffff93d419854000 (size 4096):
comm "cat", pid 23327, jiffies 4624670141 (age 495992.217s)
hex dump (first 32 bytes):
6b 66 65 6e 63 65 2d 23 32 35 30 3a 20 30 78 30 kfence-#250: 0x0
30 30 30 30 30 30 30 37 35 34 62 64 61 31 32 2d 0000000754bda12-
backtrace:
seq_read_iter+0x313/0x440
seq_read+0x14b/0x1a0
full_proxy_read+0x56/0x80
vfs_read+0xa5/0x1b0
ksys_read+0xa0/0xf0
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xa9
I find that we can easily reproduce this problem with the following commands:
cat /sys/kernel/debug/kfence/objects
echo scan > /sys/kernel/debug/kmemleak
cat /sys/kernel/debug/kmemleak
The leaked memory is allocated in the stack below:
do_syscall_64
do_sys_open
do_dentry_open
full_proxy_open
seq_open ---> alloc seq_file
vfs_read
full_proxy_read
seq_read
seq_read_iter
traverse ---> alloc seq_buf
And it should have been released in the following process:
do_syscall_64
syscall_exit_to_user_mode
exit_to_user_mode_prepare
task_work_run
____fput
__fput
full_proxy_release ---> free here
However, the release function corresponding to file_operations is not implemented in kfence. As a result, a memory leak occurs. Therefore, the solution to this problem is to implement the corresponding release function.