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([2602:47:d490:6901:9d52:4fe8:10ce:5c3]) by smtp.gmail.com with ESMTPSA id c5-20020aa78c05000000b0066f37665a63sm456138pfd.73.2023.08.03.18.45.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Aug 2023 18:45:19 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Cc: joel@jms.id.au, akihiko.odaki@daynix.com, laurent@vivier.eu, deller@gmx.de Subject: [PATCH v8 02/17] linux-user: Fix MAP_FIXED_NOREPLACE on old kernels Date: Thu, 3 Aug 2023 18:45:02 -0700 Message-Id: <20230804014517.6361-3-richard.henderson@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230804014517.6361-1-richard.henderson@linaro.org> References: <20230804014517.6361-1-richard.henderson@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::42e; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x42e.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Akihiko Odaki The man page states: > Note that older kernels which do not recognize the MAP_FIXED_NOREPLACE > flag will typically (upon detecting a collision with a preexisting > mapping) fall back to a “non-MAP_FIXED” type of behavior: they will > return an address that is different from the requested address. > Therefore, backward-compatible software should check the returned > address against the requested address. https://man7.org/linux/man-pages/man2/mmap.2.html Signed-off-by: Akihiko Odaki Message-Id: <20230802071754.14876-3-akihiko.odaki@daynix.com> Signed-off-by: Richard Henderson --- linux-user/mmap.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/linux-user/mmap.c b/linux-user/mmap.c index a11c630a7b..90b3ef2140 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -263,7 +263,11 @@ static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last, void *p = mmap(host_start, qemu_host_page_size, target_to_host_prot(prot), flags | MAP_ANONYMOUS, -1, 0); - if (p == MAP_FAILED) { + if (p != host_start) { + if (p != MAP_FAILED) { + munmap(p, qemu_host_page_size); + errno = EEXIST; + } return false; } prot_old = prot; @@ -687,17 +691,25 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot, /* map the middle (easier) */ if (real_start < real_last) { - void *p; + void *p, *want_p; off_t offset1; + size_t len1; if (flags & MAP_ANONYMOUS) { offset1 = 0; } else { offset1 = offset + real_start - start; } - p = mmap(g2h_untagged(real_start), real_last - real_start + 1, - target_to_host_prot(target_prot), flags, fd, offset1); - if (p == MAP_FAILED) { + len1 = real_last - real_start + 1; + want_p = g2h_untagged(real_start); + + p = mmap(want_p, len1, target_to_host_prot(target_prot), + flags, fd, offset1); + if (p != want_p) { + if (p != MAP_FAILED) { + munmap(p, len1); + errno = EEXIST; + } goto fail; } passthrough_start = real_start;