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Mon, 22 Jan 2024 10:23:35 -0500 (EST) Message-ID: Date: Tue, 23 Jan 2024 00:23:27 +0900 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Recent-ish changes in binfmt_elf made my program segfault Content-Language: en-US To: Pedro Falcato Cc: ebiederm@xmission.com, keescook@chromium.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, linux-fsdevel@vger.kernel.org References: From: Jan Bujak In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: ClamAV using ClamSMTP X-Rspamd-Queue-Id: AA881160008 X-Rspam-User: X-Stat-Signature: 1ixa7ronrdfphm77gsgyiucw8ypona5z X-Rspamd-Server: rspam01 X-HE-Tag: 1705937026-338117 X-HE-Meta: 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 503+uxvK EWLabI0bSLvcdtKR2Masyff9E+BbC7WKUk7w4ggQqwYWH8KZt9sWC5bRi/nES4MnU48aoxJLJnKNLrOWoK8cwyEz6+kvozMH0hej0/+ud+9JI1L7c5wcA6K0WZFOmekngERyFExWqcXeZZyO8T0SxVXKs0SYr1DTh61yDL+ryPWN5Ux0PkeT0rvCyBnsXxFy4+eEPypt9zQNZ62Y/xS+OjYVR2VdR82nm3Qdp2LS9JcG/K3CF/OPiYASFgnjJsg3+cKIw4HftD2fuzcieQ4Wdux8XLo8X5tWyoH++JGPGV+Ikj9RgAqPWDmNsAbGj/2+dF4wVL4P0+CgtAubxix0Sg8jhzBKVpy+x46H41Gmtr0C3P+AzKEcrWSaMgC729pkihtqGQE+rZhYkMArHx+F2vsCXF4kG+edfG2KNfbxgEfSZusoJunqKTbpSaJRrWdddvI2A X-Bogosity: Ham, tests=bogofilter, spamicity=0.000176, 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 1/22/24 23:54, Pedro Falcato wrote: > Hi! > > Where did you get that linker script? > > FWIW, I catched this possible issue in review, and this was already > discussed (see my email and Eric's reply): > https://lore.kernel.org/all/CAKbZUD3E2if8Sncy+M2YKncc_Zh08-86W6U5wR0ZMazShxbHHA@mail.gmail.com/ > > This was my original testcase > (https://github.com/heatd/elf-bug-questionmark), which convinced the > loader to map .data over a cleared .bss. Your bug seems similar, but > does the inverse: maps .bss over .data. > I wrote the linker script myself from scratch. Thank you for the link to the previous discussion. So assuming this breakage was intended my question here is - doesn't this run afoul of the "we do not break userspace" rule?