漏洞标题
x86: 停止在profile_pc()中玩堆栈游戏
漏洞描述信息
N/A
CVSS信息
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
漏洞类别
使用共享资源的并发执行不恰当同步问题(竞争条件)
漏洞标题
x86: stop playing stack games in profile_pc()
漏洞描述信息
In the Linux kernel, the following vulnerability has been resolved:
x86: stop playing stack games in profile_pc()
The 'profile_pc()' function is used for timer-based profiling, which
isn't really all that relevant any more to begin with, but it also ends
up making assumptions based on the stack layout that aren't necessarily
valid.
Basically, the code tries to account the time spent in spinlocks to the
caller rather than the spinlock, and while I support that as a concept,
it's not worth the code complexity or the KASAN warnings when no serious
profiling is done using timers anyway these days.
And the code really does depend on stack layout that is only true in the
simplest of cases. We've lost the comment at some point (I think when
the 32-bit and 64-bit code was unified), but it used to say:
Assume the lock function has either no stack frame or a copy
of eflags from PUSHF.
which explains why it just blindly loads a word or two straight off the
stack pointer and then takes a minimal look at the values to just check
if they might be eflags or the return pc:
Eflags always has bits 22 and up cleared unlike kernel addresses
but that basic stack layout assumption assumes that there isn't any lock
debugging etc going on that would complicate the code and cause a stack
frame.
It causes KASAN unhappiness reported for years by syzkaller [1] and
others [2].
With no real practical reason for this any more, just remove the code.
Just for historical interest, here's some background commits relating to
this code from 2006:
0cb91a229364 ("i386: Account spinlocks to the caller during profiling for !FP kernels")
31679f38d886 ("Simplify profile_pc on x86-64")
and a code unification from 2009:
ef4512882dbe ("x86: time_32/64.c unify profile_pc")
but the basics of this thing actually goes back to before the git tree.
CVSS信息
N/A
漏洞类别
N/A
漏洞标题
Linux kernel 安全漏洞
漏洞描述信息
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel 存在安全漏洞，该漏洞源于在profile_pc函数基于栈布局做出假设，这些假设在现代配置中可能不成立，导致KASAN警告。
CVSS信息
N/A
漏洞类别
其他