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charset="UTF-8" X-Rspam-User: X-Spamd-Result: default: False [2.83 / 9.00]; SORBS_IRL_BL(3.00)[209.85.166.169:from]; BAYES_HAM(-0.27)[68.00%]; BAD_REP_POLICIES(0.10)[]; MIME_GOOD(-0.10)[text/plain]; RCVD_NO_TLS_LAST(0.10)[]; MIME_TRACE(0.00)[0:+]; DMARC_POLICY_ALLOW(0.00)[google.com,reject]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; RCPT_COUNT_SEVEN(0.00)[9]; DKIM_TRACE(0.00)[google.com:+]; TO_DN_ALL(0.00)[]; ARC_SIGNED(0.00)[hostedemail.com:s=arc-20220608:i=1]; R_DKIM_ALLOW(0.00)[google.com:s=20210112]; TO_MATCH_ENVRCPT_SOME(0.00)[]; FROM_HAS_DN(0.00)[]; PREVIOUSLY_DELIVERED(0.00)[linux-mm@kvack.org]; R_SPF_ALLOW(0.00)[+ip4:209.85.128.0/17]; ARC_NA(0.00)[] X-Rspamd-Queue-Id: 3E77C80005 X-Rspamd-Server: rspam01 X-Stat-Signature: rsiy35yqzn657o49t5s7kmuj7kbubbu6 X-HE-Tag: 1670252026-292652 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: On Mon, Dec 5, 2022 at 3:50 PM Liam Howlett wrote: > * Jann Horn [221202 13:54]: > > As of commit ca57f02295f, brk() can expand ordinary file mappings (but > > not file mappings with weird flags), and I think it does it with > > insufficient locks. I think brk() probably needs some extra checks to > > make sure it's operating on a brk-like VMA (which means it should at > > least be anonymous, and perhaps pass the full can_vma_merge_after() > > check so that we're not creating unnecessary special cases?). > > > Thanks. This is probably caused by commit 2e7ce7d354f2: "mm/mmap: > change do_brk_flags() to expand existing VMA and add do_brk_munmap()" Yeah. > Specifically the checks around expanding the VMA. > > > user@vm:~/brk_stretch$ cat brk_file.c > > Thanks for the testcase. I have a fix that I'm testing, but it's worth > noting that the brk call will succeed - except a new VMA will be > created. Is this what you expect? Yes, that's what I would expect.