diff --git a/sdk/meow_jpeg.c b/sdk/meow_jpeg.c
index 0330333..82d3bc4 100644
--- a/sdk/meow_jpeg.c
+++ b/sdk/meow_jpeg.c
@@ -36,10 +36,10 @@ void meow_img_target_dims(int w, int h, int maxdim, int *tw, int *th)
 {
     if (w >= h) {
         *tw = maxdim;
-        *th = (int)((long)h * maxdim / w);
+        *th = (int)((long long)h * maxdim / w);     /* 64 位：ILP32 上 h*maxdim 会溢出 */
     } else {
         *th = maxdim;
-        *tw = (int)((long)w * maxdim / h);
+        *tw = (int)((long long)w * maxdim / h);
     }
     if (*tw < 1) *tw = 1;
     if (*th < 1) *th = 1;
@@ -390,21 +390,25 @@ static int mj_ceil_div(int a, int b) { return (a + b - 1) / b; }
  * 这种图上 stb 旧路径的峰值本来就受控，直接交回它，档位对外表现不变。 */
 static int mj_pick_n(int longside, int maxdim)
 {
-    int n = (8 * maxdim + longside - 1) / longside;
+    long long n = ((long long)8 * maxdim + longside - 1) / longside;   /* 64 位：maxdim 可到 INT_MAX */
     if (n < 1) n = 1;
     if (n > 7) return 0;
-    return n;
+    return (int)n;
 }
 
-/* 按各分量当前的 n 计算块网格与平面尺寸，返回平面总字节。 */
-static unsigned mj_layout(mj_img *img)
+/* 按各分量当前的 n 计算块网格与平面尺寸，返回平面总字节。
+ * 返回 64 位：ILP32 上单平面 pw*ph 与 3 个平面之和都可能越过 2^32。
+ * MJ_LAYOUT_BAD 表示该乘积在 32 位 size_t 上无法表示（调用方直接拒绝）。 */
+#define MJ_LAYOUT_BAD ((unsigned long long)-1)
+static unsigned long long mj_layout(mj_img *img)
 {
-    unsigned total = 0;
+    unsigned long long total = 0;
     int i;
     for (i = 0; i < img->ncomp; i++) {
         mj_comp *c = &img->c[i];
         int sw = mj_ceil_div(img->width * c->h, img->hmax);
         int sh = mj_ceil_div(img->height * c->v, img->vmax);
+        unsigned long long plane;
         c->ow = mj_ceil_div(sw, 8);
         c->oh = mj_ceil_div(sh, 8);
         c->pw = (img->mcus_x * c->h > c->ow ? img->mcus_x * c->h : c->ow) * c->n;
@@ -413,7 +417,9 @@ static unsigned mj_layout(mj_img *img)
         c->vh = mj_ceil_div(sh * c->n, 8);
         if (c->vw > c->pw) c->vw = c->pw;
         if (c->vh > c->ph) c->vh = c->ph;
-        total += (unsigned)c->pw * (unsigned)c->ph;
+        plane = (unsigned long long)c->pw * (unsigned long long)c->ph;
+        if (plane > (unsigned long long)(size_t)-1) return MJ_LAYOUT_BAD;
+        total += plane;
     }
     return total;
 }
@@ -421,7 +427,7 @@ static unsigned mj_layout(mj_img *img)
 static int mj_sof(mj_img *img, int marker, const unsigned char *d, int len, int maxdim)
 {
     int i, n, longside, base_n;
-    unsigned int plane_bytes, target_bytes;
+    unsigned long long plane_bytes, target_bytes;
     int tw, th;
 
     if (marker != 0xC0 && marker != 0xC1 && marker != 0xC2) return 0;   /* 算术/无损/差分 */
@@ -456,10 +462,14 @@ static int mj_sof(mj_img *img, int marker, const unsigned char *d, int len, int
     img->mcus_y = mj_ceil_div(img->height, 8 * img->vmax);
 
     meow_img_target_dims(img->width, img->height, maxdim, &tw, &th);
-    target_bytes = (unsigned)tw * (unsigned)th * 4u;
+    /* 64 位算目标图字节：ILP32 上 tw*th*4 在 tw=th=32768 时正好回绕成 0，
+     * 会让下面的预算闸失效并去 malloc(0)（M26 r1 顺手审计）。 */
+    target_bytes = (unsigned long long)(unsigned)tw * (unsigned long long)(unsigned)th * 4u;
+    if (target_bytes > MJ_PEAK_CAP) return 0;
 
     for (i = 0; i < n; i++) img->c[i].n = base_n;
     plane_bytes = mj_layout(img);
+    if (plane_bytes == MJ_LAYOUT_BAD) return 0;
 
     /* 4:4:4 的色度平面与亮度等大（正常 4:2:0 只 1/4）：亮度平面超过 400KB 时色度降一档，
      * 视觉近无损，省下的正是色度要多占的两份。 */
@@ -467,6 +477,7 @@ static int mj_sof(mj_img *img, int marker, const unsigned char *d, int len, int
         plane_bytes / 3 > 400u * 1024u) {
         for (i = 1; i < n; i++) if (img->c[i].n > 1) img->c[i].n >>= 1;
         plane_bytes = mj_layout(img);
+        if (plane_bytes == MJ_LAYOUT_BAD) return 0;
     }
 
     /* 预算 2.4MB（平面 + 目标图）：超了先降色度（亮度保持清晰），再整体降档。
@@ -474,13 +485,17 @@ static int mj_sof(mj_img *img, int marker, const unsigned char *d, int len, int
     if (plane_bytes + target_bytes > 2400u * 1024u) {
         int ch = 0;
         for (i = 1; i < n; i++) if (img->c[i].n > 1) { img->c[i].n >>= 1; ch = 1; }
-        if (ch) plane_bytes = mj_layout(img);
+        if (ch) {
+            plane_bytes = mj_layout(img);
+            if (plane_bytes == MJ_LAYOUT_BAD) return 0;
+        }
     }
     /* 最后一道防线：异常巨图整体降档（最多降到 N=1），不至于一次吃掉几十 MB。 */
     while (plane_bytes + target_bytes > MJ_PEAK_CAP && base_n > 1) {
         base_n >>= 1;
         for (i = 0; i < n; i++) if (img->c[i].n > base_n) img->c[i].n = base_n;
         plane_bytes = mj_layout(img);
+        if (plane_bytes == MJ_LAYOUT_BAD) return 0;
     }
     /* 硬闸：降到 N=1 仍超上限（畸形/超大声明尺寸，如 23 字节的 SOF 65535² → 亮度面
      * 8192² = 64MiB）直接拒绝 → 返回 0 → 回退 stb（stb 对这类文件是 KB 级安全失败）。
@@ -489,7 +504,10 @@ static int mj_sof(mj_img *img, int marker, const unsigned char *d, int len, int
 
     for (i = 0; i < n; i++) {
         mj_comp *c = &img->c[i];
-        size_t bytes = (size_t)c->pw * (size_t)c->ph;
+        unsigned long long bytes64 = (unsigned long long)c->pw * (unsigned long long)c->ph;
+        size_t bytes;
+        if (bytes64 == 0 || bytes64 > (unsigned long long)(size_t)-1) return 0;
+        bytes = (size_t)bytes64;
         c->plane = (unsigned char *)malloc(bytes);
         if (!c->plane) return 0;
         memset(c->plane, 128, bytes);       /* 中性灰底，系数累加即 IDCT */
@@ -753,7 +771,8 @@ static void mj_scan_ac_prog(mj_img *img, const mj_scan *sc)
 
 static unsigned char *mj_output(mj_img *img, int tw, int th, int rgb_mode)
 {
-    unsigned char *out = (unsigned char *)malloc((size_t)tw * th * 4);
+    unsigned long long ob = (unsigned long long)tw * (unsigned long long)th * 4u;
+    unsigned char *out;
     mj_comp *cy = &img->c[0];
     mj_comp *cb = img->ncomp >= 3 ? &img->c[1] : NULL;
     mj_comp *cr = img->ncomp >= 3 ? &img->c[2] : NULL;
@@ -761,30 +780,62 @@ static unsigned char *mj_output(mj_img *img, int tw, int th, int rgb_mode)
     const unsigned char *pb = cb ? cb->plane : NULL;
     const unsigned char *pc = cr ? cr->plane : NULL;
     int x, y;
+    if (ob == 0 || ob > (unsigned long long)(size_t)-1) return NULL;
+    out = (unsigned char *)malloc((size_t)ob);
     if (!out) return NULL;
     for (y = 0; y < th; y++) {
-        int sy = (int)((long)y * cy->vh / th);
+        /* 64 位：ILP32 上 y*vh、x*vw 都可能越过 2^31（th/vh 各 3 万量级即可） */
+        long long syl = (long long)y * cy->vh / th;
+        int sy = (int)(syl < 0 ? 0 : (syl >= (long long)cy->vh ? (long long)cy->vh - 1 : syl));
         const unsigned char *ry = py + (size_t)sy * cy->pw;
-        const unsigned char *rb = pb ? pb + (size_t)((long)y * cb->vh / th) * cb->pw : NULL;
-        const unsigned char *rc = pc ? pc + (size_t)((long)y * cr->vh / th) * cr->pw : NULL;
-        unsigned char *dst = out + (size_t)y * tw * 4;
+        const unsigned char *rb = NULL, *rc = NULL;
+        if (pb) {
+            long long s = (long long)y * cb->vh / th;
+            if (s >= (long long)cb->vh) s = (long long)cb->vh - 1;
+            if (s < 0) s = 0;
+            rb = pb + (size_t)s * cb->pw;
+        }
+        if (pc) {
+            long long s = (long long)y * cr->vh / th;
+            if (s >= (long long)cr->vh) s = (long long)cr->vh - 1;
+            if (s < 0) s = 0;
+            rc = pc + (size_t)s * cr->pw;
+        }
+        unsigned char *dst = out + (size_t)((unsigned long long)y * (unsigned long long)tw * 4u);
         for (x = 0; x < tw; x++) {
-            int yv = ry[(int)((long)x * cy->vw / tw)];
+            long long yxl = (long long)x * cy->vw / tw;
+            int yv;
+            if (yxl < 0) yxl = 0;
+            if (yxl >= (long long)cy->vw) yxl = (long long)cy->vw - 1;
+            yv = ry[(int)yxl];
             unsigned char *o = dst + (size_t)x * 4;
             if (!rb) {
                 o[0] = o[1] = o[2] = (unsigned char)yv;
                 o[3] = 255;
             } else if (rgb_mode) {
+                long long ux = (long long)x * cb->vw / tw;
+                long long vx = (long long)x * cr->vw / tw;
+                if (ux < 0) ux = 0;
+                if (ux >= (long long)cb->vw) ux = (long long)cb->vw - 1;
+                if (vx < 0) vx = 0;
+                if (vx >= (long long)cr->vw) vx = (long long)cr->vw - 1;
                 o[0] = (unsigned char)yv;
-                o[1] = rb[(int)((long)x * cb->vw / tw)];
-                o[2] = rc[(int)((long)x * cr->vw / tw)];
+                o[1] = rb[(int)ux];
+                o[2] = rc[(int)vx];
                 o[3] = 255;
             } else {
-                int u = (int)rb[(int)((long)x * cb->vw / tw)] - 128;
-                int v = (int)rc[(int)((long)x * cr->vw / tw)] - 128;
-                int r = yv + ((MJ_FIX_R * v) >> 12);
-                int g = yv - ((MJ_FIX_G * u + MJ_FIX_G2 * v) >> 12);
-                int b = yv + ((MJ_FIX_B * u) >> 12);
+                long long ux = (long long)x * cb->vw / tw;
+                long long vx = (long long)x * cr->vw / tw;
+                int u, v, r, g, b;
+                if (ux < 0) ux = 0;
+                if (ux >= (long long)cb->vw) ux = (long long)cb->vw - 1;
+                if (vx < 0) vx = 0;
+                if (vx >= (long long)cr->vw) vx = (long long)cr->vw - 1;
+                u = (int)rb[(int)ux] - 128;
+                v = (int)rc[(int)vx] - 128;
+                r = yv + ((MJ_FIX_R * v) >> 12);
+                g = yv - ((MJ_FIX_G * u + MJ_FIX_G2 * v) >> 12);
+                b = yv + ((MJ_FIX_B * u) >> 12);
                 o[0] = (unsigned char)(r < 0 ? 0 : (r > 255 ? 255 : r));
                 o[1] = (unsigned char)(g < 0 ? 0 : (g > 255 ? 255 : g));
                 o[2] = (unsigned char)(b < 0 ? 0 : (b > 255 ? 255 : b));
diff --git a/sdk/meow_png_stream.c b/sdk/meow_png_stream.c
index 4da2594..ed1a12d 100644
--- a/sdk/meow_png_stream.c
+++ b/sdk/meow_png_stream.c
@@ -22,6 +22,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdint.h>
+#include <limits.h>     /* LONG_MAX：BMP 按行 seek 的 32 位偏移上限 */
 
 /* ---------------- zlib ABI ---------------- */
 #if defined(__has_include)
@@ -59,6 +60,21 @@ extern const char *zlibVersion(void);
 #  define Z_NO_FLUSH 0
 #endif
 
+/* ---------------- ILP32 尺寸算术守卫 ----------------
+ * mipsel / arm-linux-musleabi 上 long 与 size_t 都是 32 位：把「声明尺寸 × bpp」这类
+ * 乘积直接放在 long 里会回绕成小值或 0。实测（ARM32）：54 字节 BMP 头声明 w=2^27、
+ * bpp=32 → w*bpp = 2^32 = 0 → rowsize = 0 → malloc(0) → 采样索引 row + sx*4 越界读
+ * → SIGSEGV；同一文件在 LP64 宿主返回 NULL，所以宿主测试天然看不到这类。
+ * 因此：凡「由文件头算出来的字节数/偏移」一律升到 unsigned long long 再验，
+ * 超限即返回 0，由调用方回退 stb（安全失败，与 M26 之前的行为一致）。
+ * 单边上限 1<<20（1,048,576）：远超真实 BMP/PNG 声明尺寸，同时保证行字节数
+ * （≤4 MiB）、行偏移与目标 RGBA 都不会在 32 位溢出。 */
+#define MZP_MAX_DIM (1u << 20)
+static int mzp_bytes_ok(unsigned long long n)
+{
+    return n > 0 && n <= (unsigned long long)(size_t)-1;
+}
+
 /* ---------------- 字节源 ---------------- */
 typedef struct {
     FILE *f;
@@ -202,12 +218,15 @@ static int png_emit_row(png_ctx *c)
         }
     }
     if (c->next_ty < c->th) {
-        long sy = (long)c->next_ty * (long)c->h / c->th;
-        if (sy == (long)c->y) {
-            unsigned char *o = c->out + (size_t)c->next_ty * c->tw * 4;
+        long long sy = (long long)c->next_ty * (long long)c->h / c->th;   /* 64 位：ILP32 上 *h 会溢出 */
+        if (sy == (long long)c->y) {
+            unsigned char *o = c->out +
+                (size_t)((unsigned long long)c->next_ty * (unsigned long long)c->tw * 4u);
             int tx;
             for (tx = 0; tx < c->tw; tx++) {
-                int sx = (int)((long)tx * (long)c->w / c->tw);
+                long long sxl = (long long)tx * (long long)c->w / c->tw;
+                int sx = (int)(sxl < 0 ? 0
+                                        : (sxl >= (long long)c->w ? (long long)c->w - 1 : sxl));
                 unsigned char px[4];
                 png_get_px(c, dst, sx, px);
                 o[tx * 4] = px[0]; o[tx * 4 + 1] = px[1];
@@ -315,9 +334,14 @@ int meow_png_decode_stream(FILE *f, const unsigned char *mem, size_t len,
             memset(c.cur, 0, c.rowbytes);
             for (i = 0; i < 256; i++) c.trns_a[i] = 255;
             meow_img_target_dims((int)c.w, (int)c.h, maxdim, &c.tw, &c.th);
-            c.out = (unsigned char *)malloc((size_t)c.tw * c.th * 4);
-            if (!c.out) goto done;
-            memset(c.out, 0, (size_t)c.tw * c.th * 4);
+            {
+                /* ILP32 上 tw*th*4 会回绕（32768×32768×4 = 2^32 → 0 → malloc(0) 后越界写） */
+                unsigned long long ob = (unsigned long long)c.tw * (unsigned long long)c.th * 4u;
+                if (!mzp_bytes_ok(ob)) goto done;
+                c.out = (unsigned char *)malloc((size_t)ob);
+                if (!c.out) goto done;
+                memset(c.out, 0, (size_t)ob);
+            }
             memset(&c.z, 0, sizeof c.z);
             if (inflateInit_(&c.z, zlibVersion(), (int)sizeof c.z) != Z_OK) goto done;
             c.z_ready = 1;
@@ -423,16 +447,25 @@ int meow_bmp_decode_stream(FILE *f, const unsigned char *mem, size_t len,
     if (dibsize < 40 || dibsize > sizeof dib) return 0;     /* BITMAPCOREHEADER/OS2 → stb */
     memcpy(dib, dh, 4);
     if (!ps_read(&src, dib + 4, dibsize - 4)) return 0;
-    w = (long)(int)le32(dib + 4);
-    h = (long)(int)le32(dib + 8);
     bpp = le16(dib + 14);
     compression = le32(dib + 16);
     colors = (dibsize >= 36) ? le32(dib + 32) : 0;
     if (compression != 0) return 0;                          /* RLE/BITFIELDS → stb */
-    if (w <= 0 || h == 0) return 0;
     if (bpp != 8 && bpp != 16 && bpp != 24 && bpp != 32) return 0;
-    topdown = h < 0;
-    if (h < 0) h = -h;
+    /* 声明尺寸过 32 位算术闸（M26 r1 P1）：w×bpp 与 tx×w 在 ILP32 上会回绕成小值/负数，
+     * 直接导致 malloc(0) + 越界读。h=INT_MIN 时 -h 同样溢出，故升到 long long 再取绝对值。 */
+    {
+        int wi = (int)le32(dib + 4);
+        int hi = (int)le32(dib + 8);
+        long long hll;
+        if (wi <= 0 || hi == 0) return 0;
+        topdown = hi < 0;
+        hll = topdown ? -(long long)hi : (long long)hi;
+        if ((unsigned long long)wi > MZP_MAX_DIM || hll <= 0 ||
+            (unsigned long long)hll > MZP_MAX_DIM) return 0;  /* 离奇声明尺寸 → 回退 stb */
+        w = (long)wi;
+        h = (long)hll;
+    }
     if ((long)(w > h ? w : h) <= maxdim) return 0;           /* 小图走旧入口 */
 
     if (bpp <= 8) {
@@ -446,26 +479,38 @@ int meow_bmp_decode_stream(FILE *f, const unsigned char *mem, size_t len,
         for (; i < 256; i++) pal[i][0] = pal[i][1] = pal[i][2] = 0;
     }
 
-    rowsize = (w * bpp + 31) / 32 * 4;
+    {
+        /* 行字节数 64 位算（ILP32 上 w*bpp 在 w≥2^27/bpp 时回绕成 0） */
+        unsigned long long rb = ((unsigned long long)w * bpp + 31u) / 32u * 4u;
+        if (!mzp_bytes_ok(rb)) return 0;
+        rowsize = (long)rb;                                  /* w ≤ MZP_MAX_DIM → ≤ 4 MiB */
+    }
     meow_img_target_dims((int)w, (int)h, maxdim, &tw_, &th_);
     row = (unsigned char *)malloc((size_t)rowsize);
-    out = (unsigned char *)malloc((size_t)tw_ * th_ * 4);
+    {
+        unsigned long long ob = (unsigned long long)tw_ * (unsigned long long)th_ * 4u;
+        if (mzp_bytes_ok(ob)) out = (unsigned char *)malloc((size_t)ob);
+    }
     if (!row || !out) goto done;
 
     for (int ty = 0; ty < th_; ty++) {
-        int sy = (int)((long)ty * h / th_);
-        long file_row = topdown ? sy : (h - 1 - sy);
-        long off = (long)dataoff + file_row * rowsize;
-        unsigned char *o = out + (size_t)ty * tw_ * 4;
+        long long sy = (long long)ty * h / th_;
+        long long file_row = topdown ? sy : ((long long)h - 1 - sy);
+        long long off = (long long)dataoff + file_row * (long long)rowsize;
+        unsigned char *o = out + (size_t)((unsigned long long)ty * (unsigned long long)tw_ * 4u);
         if (src.mem) {
-            if (off < 0 || (size_t)off + (size_t)rowsize > src.memlen) goto done;
-            memcpy(row, src.mem + off, (size_t)rowsize);
+            if (off < 0 ||
+                (unsigned long long)off + (unsigned long long)rowsize > (unsigned long long)src.memlen)
+                goto done;
+            memcpy(row, src.mem + (size_t)off, (size_t)rowsize);
         } else {
-            if (fseek(src.f, off, SEEK_SET) != 0) goto done;
+            if (off < 0 || off > (long long)LONG_MAX) goto done;   /* fseek 只有 32 位偏移 */
+            if (fseek(src.f, (long)off, SEEK_SET) != 0) goto done;
             if (fread(row, 1, (size_t)rowsize, src.f) != (size_t)rowsize) goto done;
         }
         for (int tx = 0; tx < tw_; tx++) {
-            int sx = (int)((long)tx * w / tw_);
+            long long sxl = (long long)tx * w / tw_;
+            int sx = (int)(sxl < 0 ? 0 : (sxl >= (long long)w ? (long long)w - 1 : sxl));
             unsigned char *p = o + (size_t)tx * 4;
             if (bpp == 24) {
                 const unsigned char *q = row + sx * 3;
diff --git a/sdk/test_meow_img_stream.c b/sdk/test_meow_img_stream.c
index 4b1534d..ab80cf8 100644
--- a/sdk/test_meow_img_stream.c
+++ b/sdk/test_meow_img_stream.c
@@ -12,6 +12,9 @@
  *   S8 内存入口 == 文件入口（逐字节），峰值同级
  *   S9 回退：CMYK JPEG（4 分量）、1bpp BMP、Adam7 交错 PNG → 后端拒绝，stb 仍成功；
  *      截断/垃圾 → NULL（不崩）
+ *   S10-S16 缩解阶/restart/DHT/tRNS/step/低熵/progressive-restart 等专项
+ *   S17 32 位尺寸算术：畸形 BMP 声明尺寸（w=2^27…、24bpp 回绕点、h=INT_MIN）与 PNG
+ *      tw*th*4 回绕点 → 一律 NULL 不崩（ILP32 崩溃回归，M26 r1 P1）
  *
  * 夹具：本文件内置生成脚本（Pillow），首次运行时写到夹具目录并执行。
  * 编译（本 sdk 目录下；--wrap 用于给 malloc/free 家族打点）：
@@ -20,6 +23,17 @@
  *       -lm -lz \
  *       -Wl,--wrap=malloc -Wl,--wrap=calloc -Wl,--wrap=realloc -Wl,--wrap=free
  * 运行：./test_meow_img_stream "$PREFIX/tmp/meow_img_stream"   （exit 0=PASS / 1=FAIL）
+ *
+ * ILP32 回归（S17 的真覆盖；宿主 LP64 的 long/size_t 是 64 位，看不到 32 位回绕崩溃）：
+ * 用 zig 的 arm-linux-musleabi 目标（与 mipsel 同数据模型：long/size_t 均 4 字节），
+ * 需要一份 32 位 libz.a（设备上的 libz.a 就是 mipsel 32 位；本机可从 zlib 源码
+ * 用同一 zig cc --target=arm-linux-musleabi -c 各 .c 后 ar 打包）。命令：
+ *   zig cc --target=arm-linux-musleabi -static -O2 -I. -Iinclude -DMEOW_UI_HOST_TEST \
+ *       -o test_meow_img_stream_arm test_meow_img_stream.c meow_ui_img.c meow_jpeg.c \
+ *       meow_png_stream.c stb_image.c -lm <libz_arm.a> \
+ *       -Wl,--wrap=malloc -Wl,--wrap=calloc -Wl,--wrap=realloc -Wl,--wrap=free
+ *   ./test_meow_img_stream_arm "$PREFIX/tmp/meow_img_stream"
+ * （aarch64 Android 设备可直跑 32 位 ARM 静态二进制；2026-11-06 实测 S1-S17 全绿。）
  */
 #define _GNU_SOURCE
 #include "meow_ui.h"
@@ -566,6 +580,60 @@ static size_t build_sof_only(unsigned char *buf, int w, int h, int ncomp)
     return p;
 }
 
+/* ---- S17 用的畸形头构造器（54 字节 BMP / 仅 IHDR 的 PNG） ---- */
+static size_t bmp_build(unsigned char *b, unsigned w, unsigned hbits, unsigned bpp)
+{
+    size_t off = 54;
+    memset(b, 0, off);
+    b[0] = 'B'; b[1] = 'M';
+    b[2] = (unsigned char)(off & 0xFF); b[3] = (unsigned char)((off >> 8) & 0xFF);
+    b[10] = (unsigned char)(off & 0xFF); b[11] = (unsigned char)((off >> 8) & 0xFF);
+    b[14] = 40;                                     /* BITMAPINFOHEADER */
+    b[18] = (unsigned char)(w & 0xFF);              b[19] = (unsigned char)((w >> 8) & 0xFF);
+    b[20] = (unsigned char)((w >> 16) & 0xFF);      b[21] = (unsigned char)((w >> 24) & 0xFF);
+    b[22] = (unsigned char)(hbits & 0xFF);          b[23] = (unsigned char)((hbits >> 8) & 0xFF);
+    b[24] = (unsigned char)((hbits >> 16) & 0xFF);  b[25] = (unsigned char)((hbits >> 24) & 0xFF);
+    b[26] = 1;                                      /* planes */
+    b[28] = (unsigned char)(bpp & 0xFF);
+    return off;
+}
+
+/* 正例对照：合法的 64×64 32bpp BMP（topdown=1 时 h 写成负数） */
+static size_t bmp_build_64(unsigned char *b, int topdown)
+{
+    const unsigned w = 64, h = 64, bpp = 32;
+    size_t n = bmp_build(b, w, topdown ? (unsigned)(-64) : h, bpp);
+    unsigned x, y;
+    b[2] = (unsigned char)((n + w * h * 4) & 0xFF);         /* 文件大小（解析器不校验） */
+    b[3] = (unsigned char)(((n + w * h * 4) >> 8) & 0xFF);
+    for (y = 0; y < h; y++)
+        for (x = 0; x < w; x++, n += 4) {
+            b[n + 0] = (unsigned char)(x * 4);
+            b[n + 1] = (unsigned char)(y * 4);
+            b[n + 2] = 0x40;
+            b[n + 3] = 0xFF;
+        }
+    return n;
+}
+
+static size_t png_ihdr_only(unsigned char *b, unsigned w, unsigned h)
+{
+    static const unsigned char sig[8] = { 0x89, 'P', 'N', 'G', '\r', '\n', 0x1a, '\n' };
+    size_t p = 0;
+    memcpy(b, sig, 8);
+    p = 8;
+    b[p++] = 0; b[p++] = 0; b[p++] = 0; b[p++] = 13;        /* IHDR 长度 */
+    memcpy(b + p, "IHDR", 4); p += 4;
+    b[p++] = (unsigned char)(w >> 24); b[p++] = (unsigned char)((w >> 16) & 0xFF);
+    b[p++] = (unsigned char)((w >> 8) & 0xFF); b[p++] = (unsigned char)(w & 0xFF);
+    b[p++] = (unsigned char)(h >> 24); b[p++] = (unsigned char)((h >> 16) & 0xFF);
+    b[p++] = (unsigned char)((h >> 8) & 0xFF); b[p++] = (unsigned char)(h & 0xFF);
+    b[p++] = 8;                  /* bit depth */
+    b[p++] = 2;                  /* color type RGB */
+    b[p++] = 0; b[p++] = 0; b[p++] = 0;
+    return p;                    /* 故意不带后续块 */
+}
+
 /* ================================================================== */
 int main(int argc, char **argv)
 {
@@ -1117,6 +1185,95 @@ int main(int argc, char **argv)
         }
     }
 
+    /* ---- S17 32 位尺寸算术（ILP32 崩溃回归，M26 r1 P1） ----
+     * 54 字节 BMP 头声明 w=2^27、bpp=32 时，ILP32 上 w*bpp = 2^32 → rowsize 回绕成 0 →
+     * malloc(0) → 采样索引 row + sx*4 越界读 → SIGSEGV。LP64 宿主不会回绕，所以本节在
+     * 宿主的价值是「契约固定」：这些声明尺寸必须一律返回 NULL（且不崩）；真正的 32 位
+     * 覆盖用法见文件头「ILP32 回归」那条交叉编译命令。 */
+    printf("[S17] 32 位尺寸算术：BMP 声明尺寸 / 采样偏移溢出（ILP32 崩溃回归）\n");
+    {
+        static const struct { const char *tag; unsigned w, hbits, bpp; int must_null; } sc[] = {
+            { "w=0x07FFFFFF bpp=32（回绕点前一点）",   0x07FFFFFFu, 1u, 32u, 1 },
+            { "w=0x08000000 bpp=32（2^27，旧代码崩点）", 0x08000000u, 1u, 32u, 1 },
+            { "w=0x10000000 bpp=32",                  0x10000000u, 1u, 32u, 1 },
+            { "w=0x40000000 bpp=32",                  0x40000000u, 1u, 32u, 1 },
+            { "w=0x0AAAAAAA bpp=24（w*24 回绕点前）",  0x0AAAAAAAu, 1u, 24u, 1 },
+            { "w=0x0AAAAAAB bpp=24（w*24 ≥ 2^32）",    0x0AAAAAABu, 1u, 24u, 1 },
+            /* 合法尺寸（≤1<<20）但无像素数据：后端必须拒绝；公开入口按设计回退 stb，
+             * stb 对截断 BMP 的行为不受本单约束，故只断言「不崩」，不要求 NULL。 */
+            { "w=1000000 bpp=32（合法尺寸但无像素数据）", 1000000u, 1u, 32u, 0 },
+            { "w=0x00100000 bpp=8（单边上限 1<<20）",    0x00100000u, 1u, 8u, 0 },
+            { "w=0x00100001 bpp=8（超单边上限）",        0x00100001u, 1u, 8u, 1 },
+            { "h=0x80000000（-INT_MIN 溢出点）",         0x01000000u, 0x80000000u, 32u, 1 },
+        };
+        for (size_t i = 0; i < sizeof sc / sizeof sc[0]; i++) {
+            unsigned char buf[54];
+            int tw = 0, th = 0;
+            unsigned char *px = NULL;
+            meow_img *im;
+            char name[200];
+            size_t base, pk;
+            char *fp = path_join("evil_dims.bmp");
+            FILE *f;
+
+            bmp_build(buf, sc[i].w, sc[i].hbits, sc[i].bpp);
+            snprintf(name, sizeof name, "%s → 后端拒绝", sc[i].tag);
+            base = peak_reset();
+            CHECK(meow_bmp_decode_stream(NULL, buf, sizeof buf, 720, &tw, &th, &px) == 0, name);
+            pk = peak_since(base);
+            CHECK(px == NULL, "拒绝时不返回像素缓冲");
+            if (sc[i].must_null) CHECK(pk < PEAK_2500KB, "越界声明在算术前就被拒（不分配）");
+
+            f = fopen(fp, "wb");
+            CHECK(f != NULL, "写畸形 BMP 到夹具目录");
+            if (f) { fwrite(buf, 1, sizeof buf, f); fclose(f); }
+
+            im = meow_img_load_file_dim(fp, 720);
+            snprintf(name, sizeof name, "%s → _dim 不崩%s", sc[i].tag,
+                     sc[i].must_null ? "且返回 NULL" : "");
+            CHECK(im == NULL || !sc[i].must_null, name);
+            meow_img_free(im);
+
+            im = meow_img_load_mem_dim(buf, (int)sizeof buf, 720);
+            snprintf(name, sizeof name, "%s → _mem_dim 不崩%s", sc[i].tag,
+                     sc[i].must_null ? "且返回 NULL" : "");
+            CHECK(im == NULL || !sc[i].must_null, name);
+            meow_img_free(im);
+            free(fp);
+        }
+
+        /* 正例对照：合法 64×64 32bpp 必须仍能解（含 h<0 的正上方行序） */
+        {
+            unsigned char *big = (unsigned char *)malloc(54 + 64 * 64 * 4);
+            int tw = 0, th = 0;
+            unsigned char *px = NULL;
+            size_t n;
+            CHECK(big != NULL, "分配正例 BMP 缓冲");
+            if (big) {
+                n = bmp_build_64(big, 0);
+                CHECK(meow_bmp_decode_stream(NULL, big, n, 32, &tw, &th, &px) == 1 &&
+                      tw == 32 && th == 32, "正例：64x64 32bpp 正序 → 32x32");
+                free(px); px = NULL; tw = th = 0;
+                n = bmp_build_64(big, 1);
+                CHECK(meow_bmp_decode_stream(NULL, big, n, 32, &tw, &th, &px) == 1 &&
+                      tw == 32 && th == 32, "正例：64x64 32bpp 倒序（h<0）→ 32x32");
+                free(px);
+                free(big);
+            }
+        }
+
+        /* PNG：tw*th*4 在 ILP32 上回绕成 0 的坐标点（65535² 头 + maxdim=32768） */
+        {
+            unsigned char pb[64];
+            int tw = 0, th = 0;
+            unsigned char *px = NULL;
+            size_t pn = png_ihdr_only(pb, 65535, 65535);
+            CHECK(meow_png_decode_stream(NULL, pb, pn, 32768, &tw, &th, &px) == 0,
+                  "PNG 65535² maxdim=32768 → 拒绝（目标图字节数会回绕）");
+            CHECK(px == NULL, "PNG 拒绝时不返回像素缓冲");
+        }
+    }
+
     /* ---- S8 内存入口 ---- */
     printf("[S8] 内存入口 meow_img_load_mem_dim\n");
     {