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fix width/height loading - lel - Farbfeld image viewer |
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git clone git://git.codemadness.org/lel |
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Log |
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Files |
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README |
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LICENSE |
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commit 315842241bfb79a764962c2ed86f24db2a5a3946 |
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parent c34f9949c648ba8fe0ca7e2230a3bb72ced5810b |
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Author: NRK <[email protected]> |
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Date: Thu, 15 Feb 2024 06:48:40 +0000 |
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fix width/height loading |
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- shift by 24 places might overflow INT_MAX (uint8_t gets |
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promoted to `int` due to integer promotion rules). cast to |
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uint32_t to fix. to reproduce: |
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[lel]~> gcc -g3 -std=c99 -Wall -pedantic -DVERSION=\"0.2\" lel.c -fsani… |
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[lel]~> printf "farbfeld\xff\xff\xff\xff\xff\xff\xff\xff" | ./lel |
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lel.c:110:80: runtime error: left shift of 255 by 24 places cannot be r… |
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lel.c:111:83: runtime error: left shift of 255 by 24 places cannot be r… |
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- the width and height would be broken on big-endian systems |
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because they are being loaded as little-endian (via the |
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shift-or construct) and then being fed to ntohl(). this works |
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on little-endian systems since ntohl does a byte swap but on |
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big-endian systems ntohl() is a no-op and will leave the |
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integer at wrong state. |
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fix by just shifting the proper byte into the right place to |
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begin with: https://commandcenter.blogspot.com/2012/04/byte-order-fallacy.html?… |
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Diffstat: |
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M lel.c | 5 ++--- |
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1 file changed, 2 insertions(+), 3 deletions(-) |
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--- |
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diff --git a/lel.c b/lel.c |
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@@ -1,5 +1,4 @@ |
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/* See LICENSE file for copyright and license details. */ |
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-#include <arpa/inet.h> |
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#include <errno.h> |
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#include <signal.h> |
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@@ -107,8 +106,8 @@ ff_open(struct img *img) |
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if (memcmp(hdr, "farbfeld", 8)) |
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return -1; |
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- img->width = ntohl((hdr[8] << 0) | (hdr[9] << 8) | (hdr[10] << 16) | (… |
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- img->height = ntohl((hdr[12] << 0) | (hdr[13] << 8) | (hdr[14] << 16) … |
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+ img->width = ((uint32_t)hdr[8] << 24) | (hdr[9] << 16) | (hdr[10] << … |
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+ img->height = ((uint32_t)hdr[12] << 24) | (hdr[13] << 16) | (hdr[14] <… |
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if (img->width <= 0 || img->height <= 0) |
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return -1; |
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