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Thu, 20 Aug 2026 16:58:20 +0000 Received: from dip154.lsn.ir2.yahoo.com ([87.248.99.163]) by hello (SMTP) with SMTP ID 8cc8ace8c40ab7de35cb50eca70dcdbd; Thu, 20 Aug 2026 16:58:15 +0000 (UTC) From: Tomasz Unger Date: Thu, 20 Aug 2026 18:58:12 +0200 Subject: [PATCH v2] staging: fbtft: prefer snprintf over sprintf in fbtft-core.c Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260820-fbtft-v2-final-v2-1-44d107b04634@yahoo.pl> X-B4-Tracking: v=1; b=H4sIAAAAAAAC/yXMwQ5FMBBA0V+RWZukZkH5FbFAp4xISdsnLxH/r liexb0nBPbCAZrsBM+HBNlcAuUZjHPvJkYxyUCKSqVJoR2ijXgQWnH9ipWuCzamMLpiSNHu2cr /Hbbd5/AbFh7jc4HrugHuaWz/cgAAAA== X-Change-ID: 20260820-fbtft-v2-final-7891edd1d87e To: Andy Shevchenko , Greg Kroah-Hartman Cc: dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org, Dan Carpenter , Tomasz Unger X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1787245094; l=2352; i=tomasz.unger@yahoo.pl; s=20260311; h=from:subject:message-id; bh=Vb6a0nlxcTQQQNTbxhFquNvqg+VCLZ0UAyF94lMD/Og=; b=3b9EtNix8VYT957kW4pB9zzHtHrNt4t4E3UKE8alsCVDA4txh9vZLbGalXj3DxNQSdGg1lsEV xjLWB+So9s7CLnmCLQeEcjRRooDjIKAl/K+75NkYzGYu08w3QnAx7tU X-Developer-Key: i=tomasz.unger@yahoo.pl; a=ed25519; pk=EPPsO91uz/0J2cTQ6ol+dgxYaieEc9dKSXWUb51n46c= References: <20260820-fbtft-v2-final-v2-1-44d107b04634.ref@yahoo.pl> Using sprintf has potential for buffer overflows if the formatted string exceeds the destination buffer size. Replace it with snprintf, passing sizeof() of the fixed-size stack buffers (text1[50] and text2[50]) so the write is always bounded. An overflow is impossible here: even the worst case for the argument types (size_t for text1, three ints for text2) still fits within 50 bytes. Use snprintf() rather than scnprintf() since the return value is not used here. Signed-off-by: Tomasz Unger --- Changes in v2 (per Dan Carpenter's review): - Switched from scnprintf() to snprintf(), since the return value is unused. - Reworded the commit message: overflow is impossible, not merely unlikely, and dropped detail about where the values come from. Verified with checkpatch.pl - no errors or warnings. Compiled the fbtft module successfully with CONFIG_FB_TFT=3Dm. fb.ko, syscopyarea.ko, sysimgblt.ko, sysfillrect.ko, fb_sys_fops.ko and fbtft.ko all load without errors in a QEMU environment (verified via insmod and lsmod, dmesg shows no errors). --- drivers/staging/fbtft/fbtft-core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/staging/fbtft/fbtft-core.c b/drivers/staging/fbtft/fbt= ft-core.c index ca0c38221c16..9ea0442a337e 100644 --- a/drivers/staging/fbtft/fbtft-core.c +++ b/drivers/staging/fbtft/fbtft-core.c @@ -784,10 +784,10 @@ int fbtft_register_framebuffer(struct fb_info *fb_inf= o) fbtft_sysfs_init(par); =20 if (par->txbuf.buf && par->txbuf.len >=3D 1024) - sprintf(text1, ", %zu KiB buffer memory", par->txbuf.len >> 10); + snprintf(text1, sizeof(text1), ", %zu KiB buffer memory", par->txbuf.len= >> 10); if (spi) - sprintf(text2, ", spi%d.%d at %d MHz", spi->controller->bus_num, - spi_get_chipselect(spi, 0), spi->max_speed_hz / 1000000); + snprintf(text2, sizeof(text2), ", spi%d.%d at %d MHz", spi->controller->= bus_num, + spi_get_chipselect(spi, 0), spi->max_speed_hz / 1000000); fb_dbg(fb_info, "%s frame buffer, %dx%d, %d KiB video memory%s, fps=3D%lu%s\n", fb_info->fix.id, fb_info->var.xres, fb_info->var.yres, --- base-commit: 8d3ae59288f1e7d58d76558a6ee96d533bc5019f change-id: 20260820-fbtft-v2-final-7891edd1d87e Best regards, -- =20 Tomasz Unger