From 6e682d53fc1ef73a169e2a5300326cb23abb32ee Mon Sep 17 00:00:00 2001 From: Gabriel Krisman Bertazi Date: Mon, 16 Mar 2020 20:45:06 -0400 Subject: [PATCH] um: ubd: Prevent buffer overrun on command completion On the hypervisor side, when completing commands and the pipe is full, we retry writing only the entries that failed, by offsetting io_req_buffer, but we don't reduce the number of bytes written, which can cause a buffer overrun of io_req_buffer, and write garbage to the pipe. Cc: Martyn Welch Signed-off-by: Gabriel Krisman Bertazi Signed-off-by: Richard Weinberger --- arch/um/drivers/ubd_kern.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c index 247f95da057b..eca45ad2166c 100644 --- a/arch/um/drivers/ubd_kern.c +++ b/arch/um/drivers/ubd_kern.c @@ -1607,7 +1607,9 @@ int io_thread(void *arg) written = 0; do { - res = os_write_file(kernel_fd, ((char *) io_req_buffer) + written, n); + res = os_write_file(kernel_fd, + ((char *) io_req_buffer) + written, + n - written); if (res >= 0) { written += res; }