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Tue, 01 Sep 2026 21:50:58 -0700 (PDT) From: Anshika Jain To: Andy Shevchenko Cc: Greg Kroah-Hartman , sashiko-bot@kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-staging@lists.linux.dev, Anshika Jain Subject: [PATCH] staging: fbtft: fix len<=0 buffer overflow in define_fbtft_write_reg() Date: Wed, 2 Sep 2026 10:20:26 +0530 Message-Id: <20260902045026.7442-1-anshikajain196872@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit If len is 0 or negative when a define_fbtft_write_reg()-generated function is called, len-- underflows to -1, causing the subsequent while (i--) loop to run approximately 2^31 times and write far past the end of buf. This is a latent bug: nothing in the current code prevents two adjacent negative values in an init_sequence from producing len=0, and there is no guarantee future or out-of-tree panel definitions won't do so. Add an early return for len <= 0, matching the existing guard already present in the sibling function fbtft_write_reg8_bus9(). Reported-by: sashiko-bot Link: https://sashiko.dev/#/patchset/20260830161529.14500-1-anshikajain196872@gmail.com?part=1 Signed-off-by: Anshika Jain --- drivers/staging/fbtft/fbtft-bus.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/staging/fbtft/fbtft-bus.c b/drivers/staging/fbtft/fbtft-bus.c index e03aa251c..7d7135571 100644 --- a/drivers/staging/fbtft/fbtft-bus.c +++ b/drivers/staging/fbtft/fbtft-bus.c @@ -20,6 +20,9 @@ void func(struct fbtft_par *par, int len, ...) \ int offset = 0; \ buffer_type *buf = (buffer_type *)par->buf; \ \ + if (len <= 0) \ + return; \ + \ if (unlikely(par->debug & DEBUG_WRITE_REGISTER)) { \ va_start(args, len); \ for (i = 0; i < len; i++) { \ -- 2.34.1