linux-kernel - Re: [tip: x86/urgent] x86/fault: Fix wrong signal when vsyscall fails with pkey

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Date:   Mon, 20 Sep 2021 16:43:55 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     linux-kernel@...r.kernel.org
Cc:     linux-tip-commits@...r.kernel.org,
        Jiashuo Liang <liangjs@....edu.cn>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org
Subject: Re: [tip: x86/urgent] x86/fault: Fix wrong signal when vsyscall
 fails with pkey

On Mon, Sep 20, 2021 at 10:42:39AM -0000, tip-bot2 for Jiashuo Liang wrote:
> The following commit has been merged into the x86/urgent branch of tip:
> 
> Commit-ID:     0829d0b6bf0fb3453608798442deaf00c4a1abec
> Gitweb:        https://git.kernel.org/tip/0829d0b6bf0fb3453608798442deaf00c4a1abec
> Author:        Jiashuo Liang <liangjs@....edu.cn>
> AuthorDate:    Fri, 30 Jul 2021 11:01:52 +08:00
> Committer:     Borislav Petkov <bp@...e.de>
> CommitterDate: Mon, 20 Sep 2021 12:31:06 +02:00
> 
> x86/fault: Fix wrong signal when vsyscall fails with pkey
> 
> The function __bad_area_nosemaphore() calls kernelmode_fixup_or_oops()
> with the parameter @signal being actually @pkey, which will send a
> signal numbered with the argument in @pkey.
> 
> This bug can be triggered when the kernel fails to access user-given
> memory pages that are protected by a pkey, so it can go down the
> do_user_addr_fault() path and pass the !user_mode() check in
> __bad_area_nosemaphore().
> 
> Most cases will simply run the kernel fixup code to make an -EFAULT. But
> when another condition current->thread.sig_on_uaccess_err is met, which
> is only used to emulate vsyscall, the kernel will generate the wrong
> signal.
> 
> Add a new parameter @pkey to kernelmode_fixup_or_oops() to fix this.
> 
>  [ bp: Massage commit message. ]
> 
> Fixes: 5042d40a264c ("x86/fault: Bypass no_context() for implicit kernel faults from usermode")
> Signed-off-by: Jiashuo Liang <liangjs@....edu.cn>
> Signed-off-by: Borislav Petkov <bp@...e.de>
> Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Link: https://lkml.kernel.org/r/20210730030152.249106-1-liangjs@pku.edu.cn
> ---
>  arch/x86/mm/fault.c | 26 ++++++++++++++++++--------
>  1 file changed, 18 insertions(+), 8 deletions(-)

Zapping it again because the 0day bot found some randconfig which fails:

https://lkml.kernel.org/r/202109202245.APvuT8BX-lkp@intel.com

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette