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Subject[PATCH 1/2] um: ubd: Prevent buffer overrun on command completion
Date
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 <martyn.welch@collabora.com>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
---
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 6627d7c30f37..0f5d0a699a49 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -1606,7 +1606,9 @@ 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;
}
--
2.25.0
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