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b=CmVx6dRzicEYeby+eqehWh43quHdNoBbYY/i36pebwlC3hu3ZmeS4VjBXURj7aNy3 iceEu2pMqBEVdzfyoNs6zYPwdeFEVjMU4daLSOF+34RPv/VgtKgm1TQzPbhCvKJCzp PwHKW3yddAFwEE2clGQPe9VCz0EWlv35PYz4PkEEkLTMMrd+GAZOMmGABmKaUl5Y8d 4udjlt3Z97dUrMWxxJyIATuY3MTqmnZM5WdZYeq2ykeLqUHwwS1ZlLE9RAdOJI4t5m dZHSPXrDPE8q2nmOH9o+Xw5o1ED5ivvKuuyvGRHdoAhgoYmdvYsWWSvRA9smcyAVNW 9J1gVzjdVbV+Q== Date: Thu, 18 Apr 2024 22:44:31 +0300 From: Mike Rapoport To: Nadav Amit Cc: Linux Kernel Mailing List , Andrew Morton , Andy Lutomirski , Arnd Bergmann , Catalin Marinas , Christoph Hellwig , Helge Deller , Lorenzo Stoakes , Luis Chamberlain , Mark Rutland , Masami Hiramatsu , Mathieu Desnoyers , Michael Ellerman , Palmer Dabbelt , Peter Zijlstra , Russell King , Song Liu , Steven Rostedt , Thomas Gleixner , Uladzislau Rezki , Will Deacon , bpf , linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, "open list:MEMORY MANAGEMENT" , linux-modules@vger.kernel.org, linux-parisc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-trace-kernel@vger.kernel.org, linuxppc-dev , the arch/x86 maintainers Subject: Re: [RFC PATCH 3/7] module: [ Message-ID: References: <20240411160526.2093408-1-rppt@kernel.org> <20240411160526.2093408-4-rppt@kernel.org> <0C4B9C1A-97DE-4798-8256-158369AF42A4@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 2375E1C0002 X-Stat-Signature: 6u9pq5omjgak4m9psexnmi9r8f5ewcut X-HE-Tag: 1713469549-642499 X-HE-Meta: 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 aSjkvHAs RsEWv/iZITHSrY3SDhAnXpCouXNRKy9YWkZ1z2l2n+V0U6X6ryOxa+keSX/h5ggeDNS7j24yPc4lDdY/onEtSaBhcrgionyI2Fn9gzo7lOSLpfV+O5vSlIoOgbMSDb3z6EzoqWLs31ujbfWMGNXXFMWGu9QoKZL461Um+knXBL7YO5ImQjCbEDpSFp6/hnFAKz1aOtIhiBBCQ7FGgayZF6BcEEq6tmK5dmpWrvjttMlKdn+OmTmjo8evceVqFxyTSupb1iZwf5040kfxEwZrBYomhiQIi3sBGjSmhUDlWYR9nf4h3pmahKPCGqmeoSlWV27T6dLxOlUcbODb5xVytvQiyz/pIR47VjECm X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Apr 18, 2024 at 10:31:16PM +0300, Nadav Amit wrote: > > > On 18 Apr 2024, at 13:20, Mike Rapoport wrote: > > > > On Tue, Apr 16, 2024 at 12:36:08PM +0300, Nadav Amit wrote: > >> > >> > >> > >> I might be missing something, but it seems a bit racy. > >> > >> IIUC, module_finalize() calls alternatives_smp_module_add(). At this > >> point, since you don’t hold the text_mutex, some might do text_poke(), > >> e.g., by enabling/disabling static-key, and the update would be > >> overwritten. No? > > > > Right :( > > Even worse, for UP case alternatives_smp_unlock() will "patch" still empty > > area. > > > > So I'm thinking about calling alternatives_smp_module_add() from an > > additional callback after the execmem_update_copy(). > > > > Does it make sense to you? > > Going over the code again - I might have just been wrong: I confused the > alternatives and the jump-label mechanisms (as they do share a lot of > code and characteristics). > > The jump-labels are updated when prepare_coming_module() is called, which > happens after post_relocation() [which means they would be updated using > text_poke() “inefficiently” but should be safe]. > > The “alternatives” appear only to use text_poke() (in contrast for > text_poke_early()) from very specific few flows, e.g., > common_cpu_up() -> alternatives_enable_smp(). > > Are those flows pose a problem after boot? Yes, common_cpu_up is called on CPU hotplug, so it's possible to have a race between alternatives_smp_module_add() and common_cpu_up() -> alternatives_enable_smp(). And in UP case alternatives_smp_module_add() will call alternatives_smp_unlock() that will patch module text before it is updated. > Anyhow, sorry for the noise. On the contrary, I would have missed it. -- Sincerely yours, Mike.