From: Borislav Petkov <bp@alien8.de>
To: "张子勋(Zhang Zixun)" <zhangzixun1@oppo.com>
Cc: "tony.luck@intel.com" <tony.luck@intel.com>,
"linux-edac@vger.kernel.org" <linux-edac@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: A stack overflow found in flags_write()
Date: Mon, 27 Dec 2021 22:15:55 +0100 [thread overview]
Message-ID: <YcotC4QE29+GGUey@zn.tnic> (raw)
In-Reply-To: <YcnePfF1OOqoQwrX@zn.tnic>
As to the issue at hand, that was a good catch - I was just able to
trigger it so I wrote a proper patch for you.
Lemme know if you're ok with it - I'll queue it soon.
Thx.
---
From: Zhang Zixun <zhang133010@icloud.com>
Date: Mon, 27 Dec 2021 22:02:49 +0100
Subject: [PATCH] x86/mce/inject: Avoid out-of-bounds write when setting flags
A contrived zero-length write, for example, by using write(2):
...
ret = write(fd, str, 0);
...
to the "flags" file causes:
BUG: KASAN: stack-out-of-bounds in flags_write
Write of size 1 at addr ffff888019be7ddf by task writefile/3787
CPU: 4 PID: 3787 Comm: writefile Not tainted 5.16.0-rc7+ #12
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
due to accessing buf one char before its start.
Prevent such out-of-bounds access.
[ bp: Productize into a proper patch. ]
Fixes: 0451d14d0561 ("EDAC, mce_amd_inj: Modify flags attribute to use string arguments")
Signed-off-by: Zhang Zixun <zhang133010@icloud.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/TY2PR02MB2815A59F6B963F9C068CBB8A8E429@TY2PR02MB2815.apcprd02.prod.outlook.com
---
arch/x86/kernel/cpu/mce/inject.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/mce/inject.c b/arch/x86/kernel/cpu/mce/inject.c
index 6eac840c64bb..5fbd7ffb3233 100644
--- a/arch/x86/kernel/cpu/mce/inject.c
+++ b/arch/x86/kernel/cpu/mce/inject.c
@@ -363,7 +363,7 @@ static ssize_t flags_write(struct file *filp, const char __user *ubuf,
char buf[MAX_FLAG_OPT_SIZE], *__buf;
int err;
- if (cnt > MAX_FLAG_OPT_SIZE)
+ if (!cnt || cnt > MAX_FLAG_OPT_SIZE)
return -EINVAL;
if (copy_from_user(&buf, ubuf, cnt))
--
2.29.2
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
prev parent reply other threads:[~2021-12-27 21:15 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <TY2PR02MB2815A59F6B963F9C068CBB8A8E429@TY2PR02MB2815.apcprd02.prod.outlook.com>
2021-12-27 15:39 ` A stack overflow found in flags_write() Borislav Petkov
2021-12-27 21:15 ` Borislav Petkov [this message]
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