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Date: Wed, 12 Jan 2022 16:27:27 -0800 From: Kees Cook <keescook@...omium.org> To: Peter Huewe <peterhuewe@....de> Cc: Kees Cook <keescook@...omium.org>, Jarkko Sakkinen <jarkko@...nel.org>, Jason Gunthorpe <jgg@...pe.ca>, linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: [PATCH] tpm: vtpm_proxy: Avoid device-originated buffer overflow When building with -Warray-bounds, this warning was emitted: In function 'memset', inlined from 'vtpm_proxy_fops_read' at drivers/char/tpm/tpm_vtpm_proxy.c:102:2: ./include/linux/fortify-string.h:43:33: warning: '__builtin_memset' pointer overflow between offset 164 and size [2147483648, 4294967295] [-Warray-bounds] 43 | #define __underlying_memset __builtin_memset | ^ There was no checking of the req_len value from the device. A malicious (or buggy) device could end up leaking (and when wiping) memory contents beyond the end of the proxy buffer. Cc: Peter Huewe <peterhuewe@....de> Cc: Jarkko Sakkinen <jarkko@...nel.org> Cc: Jason Gunthorpe <jgg@...pe.ca> Cc: linux-integrity@...r.kernel.org Signed-off-by: Kees Cook <keescook@...omium.org> --- drivers/char/tpm/tpm_vtpm_proxy.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c index 91c772e38bb5..5c865987ba5c 100644 --- a/drivers/char/tpm/tpm_vtpm_proxy.c +++ b/drivers/char/tpm/tpm_vtpm_proxy.c @@ -91,7 +91,7 @@ static ssize_t vtpm_proxy_fops_read(struct file *filp, char __user *buf, len = proxy_dev->req_len; - if (count < len) { + if (count < len || len > sizeof(proxy_dev->buffer)) { mutex_unlock(&proxy_dev->buf_lock); pr_debug("Invalid size in recv: count=%zd, req_len=%zd\n", count, len); -- 2.30.2
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