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[34.125.32.3]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-24668864426sm136937785ad.80.2025.08.27.21.17.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Aug 2025 21:17:04 -0700 (PDT) Date: Thu, 28 Aug 2025 04:16:59 +0000 From: Carlos Llamas To: "Liam R. Howlett" Cc: Andrew Morton , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pedro Falcato , kernel-team@android.com, linux-kernel@vger.kernel.org, "open list:MEMORY MAPPING" Subject: Re: [PATCH] mm/mremap: fix regression in vrm->new_addr check Message-ID: References: <20250828032653.521314-1-cmllamas@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 5E77C1C000B X-Stat-Signature: un8xjj4h15ob3c8sqqterpoy4rdk61xn X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1756354626-901941 X-HE-Meta: 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 BHTzGqM/ LNa2+nhW/Exeu9m8gnJEcjm3kXQfogRrHewapZh/C1wZnXCfGnjUd+/rO35ZQQ9vFtHctmMgSdPI7BpNXGX+ce7lsdoZ/QZT7h4Hi6ZGzYwvtWDrwUuVzq+MJPmJHW+HF8gvZuRbdKb5rF4I0EcwSWaCSIyYZhlENJ8V8LbMTtI2XyM/5ZVBMuN1ylvv7nsnYhTdFxnre1Vup98GpPqJ+AvxkYiGarUcj1Xz1S7SqS2GWaqfkhdv1xDBdexKiETj7fi1et0SVp06ov2aRIcs13yl2kU9TkKDRDTgSGVMUwe9j/arlF4cbxsh/3nKkXziWcQTsB2mId7HdaA/Au4O7Z4Ksy/duNmXX/7VJ/peZrPnTGSlONaaE1NQ1kjpUcqSLvOP2vd1HwtDAvAQxPM2FCRt5FcUWgWSyjK3J1IEbFocKnfHFu5yFv5p0oKbnpHyEY2iY6MihL9+/vmI= 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, Aug 28, 2025 at 04:06:58AM +0000, Carlos Llamas wrote: > On Wed, Aug 27, 2025 at 11:43:39PM -0400, Liam R. Howlett wrote: > > * Carlos Llamas [250827 23:27]: > > > Commit 3215eaceca87 ("mm/mremap: refactor initial parameter sanity > > > checks") moved the sanity check for vrm->new_addr from mremap_to() to > > > check_mremap_params(). > > > > > > However, this caused a regression as vrm->new_addr is now checked even > > > when MREMAP_FIXED and MREMAP_DONTUNMAP flags are not specified. In this > > > case, vrm->new_addr can be garbage and create unexpected failures. > > > > > > Fix this by moving the new_addr check after the vrm_implies_new_addr() > > > guard. This ensures that the new_addr is only checked when the user has > > > specified one explicitly. > > > > > > Fixes: 3215eaceca87 ("mm/mremap: refactor initial parameter sanity checks") > > > Signed-off-by: Carlos Llamas > > > > I assume this showed up with clang? > > Right. > > The specific test that broke on our end was this: > https://android.googlesource.com/platform/bionic/+/HEAD/tests/__cxa_atexit_test.cpp > Although I'm not exactly sure how __cxa_atexit() implementation uses > mremap() underneath. Ok, here is the specific call to mremap() in the test: https://android.googlesource.com/platform/bionic/+/HEAD/libc/bionic/atexit.cpp#197