linux-kernel - Re: [PATCH] x86/mm: Remove broken vsyscall emulation code from the page fault code

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Date: Wed, 1 May 2024 09:43:04 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Hillf Danton <hdanton@...a.com>, Andy Lutomirski <luto@...capital.net>,
	Peter Anvin <hpa@...or.com>, Adrian Bunk <bunk@...nel.org>,
	syzbot <syzbot+83e7f982ca045ab4405c@...kaller.appspotmail.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	andrii@...nel.org, bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] x86/mm: Remove broken vsyscall emulation code from the
 page fault code


* Ingo Molnar <mingo@...nel.org> wrote:

> 
> * Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 
> > I guess that patch to rip out sig_on_uaccess_err needs to go into 6.9 and 
> > even be marked for stable, since it most definitely breaks some stuff 
> > currently. Even if that "some stuff" is pretty esoteric (ie 
> > "vsyscall=emulate" together with tracing).
> 
> Yeah - I just put it into tip:x86/urgent as-is, with the various Tested-by 
> and Acked-by tags added, and we'll send it to you later this week if all 
> goes well.

Update: added the delta patch below to the fix, because now 
'tsk' is unused in emulate_vsyscall().

Thanks,

	Ingo

 arch/x86/entry/vsyscall/vsyscall_64.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index 3b0f61b2ea6d..2fb7d53cf333 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -115,7 +115,6 @@ static bool write_ok_or_segv(unsigned long ptr, size_t size)
 bool emulate_vsyscall(unsigned long error_code,
 		      struct pt_regs *regs, unsigned long address)
 {
-	struct task_struct *tsk;
 	unsigned long caller;
 	int vsyscall_nr, syscall_nr, tmp;
 	long ret;
@@ -166,8 +165,6 @@ bool emulate_vsyscall(unsigned long error_code,
 		goto sigsegv;
 	}
 
-	tsk = current;
-
 	/*
 	 * Check for access_ok violations and find the syscall nr.
 	 *