From e0c58720bfd8c0553f170b64717278b07438d2f5 Mon Sep 17 00:00:00 2001 From: Manos Pitsidianakis Date: Tue, 21 Nov 2023 11:38:39 +0200 Subject: [PATCH] ui/pixman-minimal.h: fix empty allocation MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit In the minimal pixman API stub that is used when the real pixman dependency is missing a NULL dereference happens when virtio-gpu-rutabaga allocates a pixman image with bits = NULL and rowstride_bytes = zero. A buffer of rowstride_bytes * height is allocated which is NULL. However, in that scenario pixman calculates a new stride value based on given width, height and format size. This commit adds a helper function that performs the same logic as pixman. Signed-off-by: Manos Pitsidianakis Reviewed-by: Marc-André Lureau Message-Id: <20231121093840.2121195-1-manos.pitsidianakis@linaro.org> --- include/ui/pixman-minimal.h | 48 +++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 46 insertions(+), 2 deletions(-) diff --git a/include/ui/pixman-minimal.h b/include/ui/pixman-minimal.h index efcf570c9e..6dd7de1c7e 100644 --- a/include/ui/pixman-minimal.h +++ b/include/ui/pixman-minimal.h @@ -113,6 +113,45 @@ typedef struct pixman_color { uint16_t alpha; } pixman_color_t; +static inline uint32_t *create_bits(pixman_format_code_t format, + int width, + int height, + int *rowstride_bytes) +{ + int stride = 0; + size_t buf_size = 0; + int bpp = PIXMAN_FORMAT_BPP(format); + + /* + * Calculate the following while checking for overflow truncation: + * stride = ((width * bpp + 0x1f) >> 5) * sizeof(uint32_t); + */ + + if (unlikely(__builtin_mul_overflow(width, bpp, &stride))) { + return NULL; + } + + if (unlikely(__builtin_add_overflow(stride, 0x1f, &stride))) { + return NULL; + } + + stride >>= 5; + + stride *= sizeof(uint32_t); + + if (unlikely(__builtin_mul_overflow((size_t) height, + (size_t) stride, + &buf_size))) { + return NULL; + } + + if (rowstride_bytes) { + *rowstride_bytes = stride; + } + + return g_malloc0(buf_size); +} + static inline pixman_image_t *pixman_image_create_bits(pixman_format_code_t format, int width, int height, @@ -123,13 +162,18 @@ static inline pixman_image_t *pixman_image_create_bits(pixman_format_code_t form i->width = width; i->height = height; - i->stride = rowstride_bytes ?: width * DIV_ROUND_UP(PIXMAN_FORMAT_BPP(format), 8); i->format = format; if (bits) { i->data = bits; } else { - i->free_me = i->data = g_malloc0(rowstride_bytes * height); + i->free_me = i->data = + create_bits(format, width, height, &rowstride_bytes); + if (width && height) { + assert(i->data); + } } + i->stride = rowstride_bytes ? rowstride_bytes : + width * DIV_ROUND_UP(PIXMAN_FORMAT_BPP(format), 8); i->ref_count = 1; return i; -- 2.11.0