From: Borislav Petkov <bp@alien8.de>
To: Andy Lutomirski <luto@kernel.org>
Cc: x86@kernel.org, LKML <linux-kernel@vger.kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Yonghong Song <yhs@fb.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 10/11] x86/fault: Don't run fixups for SMAP violations
Date: Wed, 3 Feb 2021 20:50:24 +0100 [thread overview]
Message-ID: <20210203195024.GK13819@zn.tnic> (raw)
In-Reply-To: <416aa53570523f2659edf9e39d553160cb253c5f.1612113550.git.luto@kernel.org>
On Sun, Jan 31, 2021 at 09:24:41AM -0800, Andy Lutomirski wrote:
> A SMAP-violating kernel access is not a recoverable condition. Imagine
> kernel code that, outside of a uaccess region, dereferences a pointer to
> the user range by accident. If SMAP is on, this will reliably generate
> as an intentional user access. This makes it easy for bugs to be
> overlooked if code is inadequately tested both with and without SMAP.
>
> We discovered this because BPF can generate invalid accesses to user
> memory, but those warnings only got printed if SMAP was off. With this
> patch, this type of error will be discovered with SMAP on as well.
>
> Cc: Yonghong Song <yhs@fb.com>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
> arch/x86/mm/fault.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 04cc98ec2423..d39946ad8a91 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -1242,7 +1242,11 @@ void do_user_addr_fault(struct pt_regs *regs,
> !(error_code & X86_PF_USER) &&
> !(regs->flags & X86_EFLAGS_AC)))
> {
^
Might wanna fix that opening brace too.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2021-02-03 19:51 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-31 17:24 [PATCH 00/11] x86/fault: Cleanups and robustifications Andy Lutomirski
2021-01-31 17:24 ` [PATCH 01/11] x86/fault: Fix AMD erratum #91 errata fixup for user code Andy Lutomirski
2021-02-01 9:05 ` Christoph Hellwig
2021-02-01 20:31 ` Borislav Petkov
2021-01-31 17:24 ` [PATCH 02/11] x86/fault: Fold mm_fault_error() into do_user_addr_fault() Andy Lutomirski
2021-01-31 17:24 ` [PATCH 03/11] x86/fault/32: Move is_f00f_bug() do do_kern_addr_fault() Andy Lutomirski
2021-02-03 14:44 ` Borislav Petkov
2021-01-31 17:24 ` [PATCH 04/11] x86/fault: Document the locking in the fault_signal_pending() path Andy Lutomirski
2021-01-31 17:24 ` [PATCH 05/11] x86/fault: Correct a few user vs kernel checks wrt WRUSS Andy Lutomirski
2021-02-03 15:48 ` Borislav Petkov
2021-01-31 17:24 ` [PATCH 06/11] x86/fault: Improve kernel-executing-user-memory handling Andy Lutomirski
2021-02-01 9:08 ` Christoph Hellwig
2021-02-02 1:00 ` Andy Lutomirski
2021-02-03 16:01 ` Borislav Petkov
2021-02-03 16:23 ` Borislav Petkov
2021-01-31 17:24 ` [PATCH 07/11] x86/fault: Split the OOPS code out from no_context() Andy Lutomirski
2021-02-03 18:56 ` Borislav Petkov
2021-02-03 19:29 ` Andy Lutomirski
2021-02-03 19:46 ` Borislav Petkov
2021-02-09 20:09 ` Andy Lutomirski
2021-01-31 17:24 ` [PATCH 08/11] x86/fault: Bypass no_context() for implicit kernel faults from usermode Andy Lutomirski
2021-01-31 17:24 ` [PATCH 09/11] x86/fault: Rename no_context() to kernelmode_fixup_or_oops() Andy Lutomirski
2021-02-01 9:14 ` Christoph Hellwig
2021-02-02 1:01 ` Andy Lutomirski
2021-02-03 19:39 ` Borislav Petkov
2021-02-03 19:53 ` Andy Lutomirski
2021-02-03 20:07 ` Borislav Petkov
2021-02-03 20:14 ` Andy Lutomirski
2021-02-03 20:25 ` Borislav Petkov
2021-01-31 17:24 ` [PATCH 10/11] x86/fault: Don't run fixups for SMAP violations Andy Lutomirski
2021-02-03 19:50 ` Borislav Petkov [this message]
2021-01-31 17:24 ` [PATCH 11/11] x86/fault: Don't look for extable entries for SMEP violations Andy Lutomirski
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