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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id c2-20020aa78802000000b00687087d8bc3sm2557075pfo.141.2023.08.10.22.45.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Aug 2023 22:45:35 -0700 (PDT) From: Kees Cook To: Petr Mladek Cc: Kees Cook , Sergey Senozhatsky , Steven Rostedt , John Ogness , Vijay Balakrishna , stable@vger.kernel.org, Tony Luck , "Guilherme G. Piccoli" , "Paul E. McKenney" , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH] printk: ringbuffer: Fix truncating buffer size min_t cast Date: Thu, 10 Aug 2023 22:45:32 -0700 Message-Id: <20230811054528.never.165-kees@kernel.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1390; i=keescook@chromium.org; h=from:subject:message-id; bh=LSsQlfVwJGANZC4BMOlstWxt7EAJ8V19cSaVUMG+hnA=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBk1cr8i9Tw8GnNz3kTm1mkiIrZuI7bebooN5tFQ YTs1cel/WeJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZNXK/AAKCRCJcvTf3G3A JqK9D/4hSDCX6PHtUGQaGrmuI0S5HitVkvLsSFBNe+yoYZStF8nq/g9woA7dMsmU3ypkEM+DRLO l9dXpbwr6JTWsjkCECKWqZjA29PjXGG8bkgkQrpVWWQWuy0Rg4h8EnsfuuVJEGtbU8U4Vlmlv2w DTytv5P8uyalfVbyF1UaEAt/PhCvZpu/UJo5xyYwO2IXSG68ouUHeN+8kCKCnlu/a3Sd66lR4Fp PEYJAG9WkSVfQ8i4vM4c7I5eke7YNosDJ0umAuPgZ2oOQlABn0ZeDmjPVbYCqfzUseB9ycnmkBa 7yVK8LPcupe+IcUA8sS0VBNN3pZQrb/2mE/PwX/0e+ZVTu/ROfugMBfGqNJwSqim44ROSFJeUek gslo9slDbwJt5EixSB4xtPWfs3AHEG3GQkzp/sIBNMHHzjJRT5GFk65/qWpnQhzlG5IMe57xFHM xOVdwl+VeevpJAAly9QrGDl7tR6xyC4Pia+sgvlIKATvpmPTziSBt/X32h8/vtOpbyvli9O/idy LJzwBKtdr9dI2ynun4ZQHr5QvD2j9w0NGmojOIJ0OTXBCZ45ZDF32r/qqjXwd06jtK70FlApiUX Wy9/1LA5N8VsjPT2HqFYXTpxS6BTHSD5VSvYhCEYhkeNcFHjkx5EzKdQyN/sv+vbDNh7MO0Nzjp RpC5fZy dRA1n43A== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org If an output buffer size exceeded U16_MAX, the min_t(u16, ...) cast in copy_data() was causing writes to truncate. This manifested as output bytes being skipped, seen as %NUL bytes in pstore dumps when the available record size was larger than 65536. Fix the cast to no longer truncate the calculation. Cc: Petr Mladek Cc: Sergey Senozhatsky Cc: Steven Rostedt Cc: John Ogness Reported-by: Vijay Balakrishna Closes: https://lore.kernel.org/lkml/d8bb1ec7-a4c5-43a2-9de0-9643a70b899f@linux.microsoft.com/ Fixes: b6cf8b3f3312 ("printk: add lockless ringbuffer") Cc: stable@vger.kernel.org Signed-off-by: Kees Cook Tested-by: Vijay Balakrishna Tested-by: Guilherme G. Piccoli # Steam Deck Reviewed-by: Tyler Hicks (Microsoft) Tested-by: Tyler Hicks (Microsoft) Reviewed-by: John Ogness Reviewed-by: Sergey Senozhatsky Reviewed-by: Petr Mladek --- kernel/printk/printk_ringbuffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index 2dc4d5a1f1ff..fde338606ce8 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -1735,7 +1735,7 @@ static bool copy_data(struct prb_data_ring *data_ring, if (!buf || !buf_size) return true; - data_size = min_t(u16, buf_size, len); + data_size = min_t(unsigned int, buf_size, len); memcpy(&buf[0], data, data_size); /* LMM(copy_data:A) */ return true;