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([203.30.3.188]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7127af416fbsm7382814b3a.207.2024.08.19.22.08.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Aug 2024 22:08:59 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Cc: gaosong@loongson.cn, philmd@linaro.org, imp@bsdimp.com, qemu-stable@nongnu.org Subject: [PATCH v2 1/2] linux-user: Handle short reads in mmap_h_gt_g Date: Tue, 20 Aug 2024 15:08:47 +1000 Message-ID: <20240820050848.165253-2-richard.henderson@linaro.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240820050848.165253-1-richard.henderson@linaro.org> References: <20240820050848.165253-1-richard.henderson@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2001:4860:4864:20::35; envelope-from=richard.henderson@linaro.org; helo=mail-oa1-x35.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=unavailable 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+patch=linaro.org@nongnu.org Sender: qemu-devel-bounces+patch=linaro.org@nongnu.org In particular, if an image has a large bss, we can hit EOF before reading all host_len bytes of the mapping. Create a helper, mmap_pread to handle the job for both the larger block in mmap_h_gt_g itself, as well as the smaller block in mmap_frag. Cc: qemu-stable@nongnu.org Fixes: eb5027ac618 ("linux-user: Split out mmap_h_gt_g") Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2504 Signed-off-by: Richard Henderson --- linux-user/mmap.c | 44 ++++++++++++++++++++++++++++++++++++++------ 1 file changed, 38 insertions(+), 6 deletions(-) diff --git a/linux-user/mmap.c b/linux-user/mmap.c index 6418e811f6..e4bf5d5f39 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -283,6 +283,40 @@ static int do_munmap(void *addr, size_t len) return munmap(addr, len); } +/* + * Perform a pread on behalf of target_mmap. We can reach EOF, we can be + * interrupted by signals, and in general there's no good error return path. + * If @zero, zero the rest of the block at EOF. + * Return true on success. + */ +static bool mmap_pread(int fd, void *p, size_t len, off_t offset, bool zero) +{ + while (1) { + ssize_t r = pread(fd, p, len, offset); + + if (likely(r == len)) { + /* Complete */ + return true; + } + if (r == 0) { + /* EOF */ + if (zero) { + memset(p, 0, len); + } + return true; + } + if (r > 0) { + /* Short read */ + p += r; + len -= r; + offset += r; + } else if (errno != EINTR) { + /* Error */ + return false; + } + } +} + /* * Map an incomplete host page. * @@ -357,10 +391,9 @@ static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last, /* Read or zero the new guest pages. */ if (flags & MAP_ANONYMOUS) { memset(g2h_untagged(start), 0, last - start + 1); - } else { - if (pread(fd, g2h_untagged(start), last - start + 1, offset) == -1) { - return false; - } + } else if (!mmap_pread(fd, g2h_untagged(start), last - start + 1, + offset, true)) { + return false; } /* Put final protection */ @@ -853,8 +886,7 @@ static abi_long mmap_h_gt_g(abi_ulong start, abi_ulong len, } if (misaligned_offset) { - /* TODO: The read could be short. */ - if (pread(fd, p, host_len, offset + real_start - start) != host_len) { + if (!mmap_pread(fd, p, host_len, offset + real_start - start, false)) { do_munmap(p, host_len); return -1; }