From c6f9076c7425cc819a0e4df748f5fe18d9f86ec8 Mon Sep 17 00:00:00 2001 From: Zhang Zixun Date: Wed, 27 Apr 2022 11:12:10 +0800 Subject: [PATCH] x86/mce/inject: Avoid out-of-bounds write when setting flags stable inclusion from stable-v5.10.94 commit 595e1ec55b307d232f8672ccbe6c84089b277b43 bugzilla: https://gitee.com/openeuler/kernel/issues/I531X9 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=595e1ec55b307d232f8672ccbe6c84089b277b43 -------------------------------- [ Upstream commit de768416b203ac84e02a757b782a32efb388476f ] 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. Link below is the next best thing because the original mail didn't get archived on lore. ] Fixes: 0451d14d0561 ("EDAC, mce_amd_inj: Modify flags attribute to use string arguments") Signed-off-by: Zhang Zixun Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/linux-edac/YcnePfF1OOqoQwrX@zn.tnic/ Signed-off-by: Sasha Levin Signed-off-by: Zheng Zengkai Acked-by: Xie XiuQi --- 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 3a44346f2276..e7808309d471 100644 --- a/arch/x86/kernel/cpu/mce/inject.c +++ b/arch/x86/kernel/cpu/mce/inject.c @@ -347,7 +347,7 @@ 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)) -- GitLab