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[2001:8b0:1d0::2]) by smtp.gmail.com with ESMTPSA id a26-20020a5d457a000000b00316eb7770b8sm3097631wrc.5.2023.08.18.08.10.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Aug 2023 08:10:59 -0700 (PDT) From: Peter Maydell To: qemu-devel@nongnu.org Cc: Gerd Hoffmann , =?utf-8?q?Marc-Andr=C3=A9_Lureau?= , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= Subject: [PATCH 2/3] ui/vnc-enc-hextile: Use static rather than dynamic length stack array Date: Fri, 18 Aug 2023 16:10:56 +0100 Message-Id: <20230818151057.1541189-3-peter.maydell@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230818151057.1541189-1-peter.maydell@linaro.org> References: <20230818151057.1541189-1-peter.maydell@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2a00:1450:4864:20::436; envelope-from=peter.maydell@linaro.org; helo=mail-wr1-x436.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 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+patch=linaro.org@nongnu.org Sender: qemu-devel-bounces+patch=linaro.org@nongnu.org In the send_hextile_tile_* function we create a variable length array data[]. In fact we know that the client_pf.bytes_per_pixel is at most 4 (enforced by set_pixel_format()), so we can make the array a compile-time fixed length of 1536 bytes. The codebase has very few VLAs, and if we can get rid of them all we can make the compiler error on new additions. This is a defensive measure against security bugs where an on-stack dynamic allocation isn't correctly size-checked (e.g. CVE-2021-3527). Signed-off-by: Peter Maydell Reviewed-by: Philippe Mathieu-Daudé --- ui/vnc-enc-hextile-template.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/ui/vnc-enc-hextile-template.h b/ui/vnc-enc-hextile-template.h index 0c56262afff..283c0eaefaf 100644 --- a/ui/vnc-enc-hextile-template.h +++ b/ui/vnc-enc-hextile-template.h @@ -7,6 +7,8 @@ #define NAME BPP #endif +#define MAX_CLIENT_BPP 4 + static void CONCAT(send_hextile_tile_, NAME)(VncState *vs, int x, int y, int w, int h, void *last_bg_, @@ -25,10 +27,13 @@ static void CONCAT(send_hextile_tile_, NAME)(VncState *vs, int bg_count = 0; int fg_count = 0; int flags = 0; - uint8_t data[(vs->client_pf.bytes_per_pixel + 2) * 16 * 16]; + uint8_t data[(MAX_CLIENT_BPP + 2) * 16 * 16]; int n_data = 0; int n_subtiles = 0; + /* Enforced by set_pixel_format() */ + assert(vs->client_pf.bytes_per_pixel <= MAX_CLIENT_BPP); + for (j = 0; j < h; j++) { for (i = 0; i < w; i++) { switch (n_colors) { @@ -205,6 +210,7 @@ static void CONCAT(send_hextile_tile_, NAME)(VncState *vs, } } +#undef MAX_CLIENT_BPP #undef NAME #undef pixel_t #undef CONCAT_I