From dd0439e1496ad326dcaa7dc67f91f2e6f6c4930b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Date: Fri, 18 Aug 2023 16:10:57 +0100 Subject: [PATCH] ui/vnc-enc-tight: Avoid dynamic stack allocation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Use autofree heap allocation instead of variable-length array on the stack. 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: Philippe Mathieu-Daudé [PMM: expanded commit message] Signed-off-by: Peter Maydell Reviewed-by: Francisco Iglesias Reviewed-by: Marc-André Lureau Message-Id: <20230818151057.1541189-4-peter.maydell@linaro.org> --- ui/vnc-enc-tight.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/ui/vnc-enc-tight.c b/ui/vnc-enc-tight.c index ee853dcfcb..41f559eb83 100644 --- a/ui/vnc-enc-tight.c +++ b/ui/vnc-enc-tight.c @@ -1097,13 +1097,13 @@ static int send_palette_rect(VncState *vs, int x, int y, switch (vs->client_pf.bytes_per_pixel) { case 4: { - size_t old_offset, offset; - uint32_t header[palette_size(palette)]; + size_t old_offset, offset, palette_sz = palette_size(palette); + g_autofree uint32_t *header = g_new(uint32_t, palette_sz); struct palette_cb_priv priv = { vs, (uint8_t *)header }; old_offset = vs->output.offset; palette_iter(palette, write_palette, &priv); - vnc_write(vs, header, sizeof(header)); + vnc_write(vs, header, palette_sz * sizeof(uint32_t)); if (vs->tight->pixel24) { tight_pack24(vs, vs->output.buffer + old_offset, colors, &offset); @@ -1115,11 +1115,12 @@ static int send_palette_rect(VncState *vs, int x, int y, } case 2: { - uint16_t header[palette_size(palette)]; + size_t palette_sz = palette_size(palette); + g_autofree uint16_t *header = g_new(uint16_t, palette_sz); struct palette_cb_priv priv = { vs, (uint8_t *)header }; palette_iter(palette, write_palette, &priv); - vnc_write(vs, header, sizeof(header)); + vnc_write(vs, header, palette_sz * sizeof(uint16_t)); tight_encode_indexed_rect16(vs->tight->tight.buffer, w * h, palette); break; }