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[222.152.189.137]) by smtp.gmail.com with ESMTPSA id x13sm13379004pjh.30.2021.06.20.20.18.38 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sun, 20 Jun 2021 20:18:49 -0700 (PDT) Subject: Re: [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack To: Linus Torvalds References: <87sg1p30a1.fsf@disp2133> <87pmwsytb3.fsf@disp2133> <87sg1lwhvm.fsf@disp2133> <6e47eff8-d0a4-8390-1222-e975bfbf3a65@gmail.com> <924ec53c-2fd9-2e1c-bbb1-3fda49809be4@gmail.com> <87eed4v2dc.fsf@disp2133> <5929e116-fa61-b211-342a-c706dcb834ca@gmail.com> <87fsxjorgs.fsf@disp2133> <87zgvqor7d.fsf_-_@disp2133> <87mtrpg47k.fsf@disp2133> <87pmwlek8d.fsf_-_@disp2133> <87k0mtek4n.fsf_-_@disp2133> <393c37de-5edf-effc-3d06-d7e63f34a317@gmail.com> Cc: "Eric W. Biederman" , linux-arch , Jens Axboe , Oleg Nesterov , Al Viro , Linux Kernel Mailing List , Richard Henderson , Ivan Kokshaysky , Matt Turner , alpha , Geert Uytterhoeven , linux-m68k , Arnd Bergmann , Ley Foon Tan , Tejun Heo , Kees Cook From: Michael Schmitz Message-ID: <60c0fe00-b966-6385-d348-f6dd45277113@gmail.com> Date: Mon, 21 Jun 2021 15:18:35 +1200 User-Agent: Mozilla/5.0 (X11; Linux ppc; rv:45.0) Gecko/20100101 Icedove/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Linus, Am 21.06.2021 um 14:17 schrieb Linus Torvalds: > On Sun, Jun 20, 2021 at 7:01 PM Michael Schmitz wrote: >> >> instrumenting get_reg on m68k and using a similar patch to yours to warn >> when unsaved registers are accessed on the switch stack, I get a hit >> from getegid and getegid32, just by running a simple ptrace on ls. >> >> Going to wack those two moles now ... > > I don't see what's going on. Those system calls don't use the register > state, afaik. What's the call chain, exactly? This is what I get from WARN_ONCE: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 1177 at arch/m68k/kernel/ptrace.c:91 get_reg+0x90/0xb8 Modules linked in: CPU: 0 PID: 1177 Comm: strace Not tainted 5.13.0-rc1-atari-fpuemu-exitfix+ #1146 Stack from 014b7f04: 014b7f04 00336401 00336401 000278f0 0032c015 0000005b 00000005 0002795a 0032c015 0000005b 0000338c 00000009 00000000 00000000 ffffffe4 00000005 00000003 00000014 00000003 00000014 efc2b90c 0000338c 0032c015 0000005b 00000009 00000000 efc2b908 00912540 efc2b908 000034cc 00912540 00000005 00000000 efc2b908 00000003 00912540 8000110c c010b0a4 efc2b90c 0002d1d8 00912540 00000003 00000014 efc2b908 0000049a 00000014 efc2b908 800acaa8 Call Trace: [<000278f0>] __warn+0x9e/0xb4 [<0002795a>] warn_slowpath_fmt+0x54/0x62 [<0000338c>] get_reg+0x90/0xb8 [<0000338c>] get_reg+0x90/0xb8 [<000034cc>] arch_ptrace+0x7e/0x250 [<0002d1d8>] sys_ptrace+0x232/0x2f8 [<00002ab6>] syscall+0x8/0xc [<0000c00b>] lower+0x7/0x20 ---[ end trace ee4be53b94695793 ]--- Syscall numbers are actually 90 and 192 - sys_old_mmap and sys_mmap2 on m68k. Used the calculator on my Ubuntu desktop, that appears to be a little confused about hex to decimal conversions. I hope that makes more sense? Cheers, Michael > > Linus >