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Message-ID: <ff5ad474-6d32-8bf8-e297-ed71a967d27c@icdsoft.com>
Date:   Tue, 29 Nov 2022 13:19:41 +0200
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Subject: Re: [tip: x86/fpu] x86/fpu/xstate: Define new functions for clearing
 fpregs and xstates
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To:     Thomas Gleixner <tglx@linutronix.de>,
        "Yu, Yu-cheng" <yu-cheng.yu@intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Cc:     linux-tip-commits@vger.kernel.org,
        Fenghua Yu <fenghua.yu@intel.com>,
        Borislav Petkov <bp@suse.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Tony Luck <tony.luck@intel.com>, x86 <x86@kernel.org>,
        "Shankar, Ravi V" <ravi.v.shankar@intel.com>
References: <20200512145444.15483-6-yu-cheng.yu@intel.com>
 <158964181793.17951.15480349640697746223.tip-bot2@tip-bot2>
 <CALCETrXfLbsrBX42Y094YLWTG=pqkrf+aSCLruCGzqnZ0Y=P-Q@mail.gmail.com>
 <10a553a5-699f-6921-705e-9afa1a8e42de@intel.com>
 <87y2c28zir.ffs@nanos.tec.linutronix.de>
From:   Ivan Zahariev <famzah@icdsoft.com>
In-Reply-To: <87y2c28zir.ffs@nanos.tec.linutronix.de>
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Hello gentlemen,
Hello Yu-cheng Yu,

Can you please take a look into this bug which syzbot tracked to a 
commit of yours (b860eb8dce5906b14e3a7f3c771e0b3d6ef61b94). Even since 
we switched from kernel 4.14 to 5.15 we are experiencing often random 
segmentation faults with the following error in "dmesg":

    post.sh[2237] bad frame in rt_sigreturn frame:00007ad24b2f8df8 
ip:733cfa4351d1 sp:7ad24b2f9398 orax:ffffffffffffffff in 
libc-2.28.so[733cfa36d000+147000]

Most commonly Bash is getting hit by this problem but other binaries 
also experience the it less often.

Thomas Gleixner has already provided some insight and a simple 
reproducer: 
https://groups.google.com/g/syzkaller-bugs/c/rbdQkahfwE4/m/RyWIrlA0BQAJ

If there is no simple fix, can we simply revert the faulty commit?

Best regards.
--Ivan