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    Subject[PATCH 5.19 147/365] NTB: ntb_tool: uninitialized heap data in tool_fn_write()
    Date
    From: Dan Carpenter <dan.carpenter@oracle.com>

    commit 45e1058b77feade4e36402828bfe3e0d3363177b upstream.

    The call to:

    ret = simple_write_to_buffer(buf, size, offp, ubuf, size);

    will return success if it is able to write even one byte to "buf".
    The value of "*offp" controls which byte. This could result in
    reading uninitialized data when we do the sscanf() on the next line.

    This code is not really desigined to handle partial writes where
    *offp is non-zero and the "buf" is preserved and re-used between writes.
    Just ban partial writes and replace the simple_write_to_buffer() with
    copy_from_user().

    Fixes: 578b881ba9c4 ("NTB: Add tool test client")
    Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
    Signed-off-by: Jon Mason <jdmason@kudzu.us>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/ntb/test/ntb_tool.c | 8 +++++---
    1 file changed, 5 insertions(+), 3 deletions(-)

    --- a/drivers/ntb/test/ntb_tool.c
    +++ b/drivers/ntb/test/ntb_tool.c
    @@ -367,14 +367,16 @@ static ssize_t tool_fn_write(struct tool
    u64 bits;
    int n;

    + if (*offp)
    + return 0;
    +
    buf = kmalloc(size + 1, GFP_KERNEL);
    if (!buf)
    return -ENOMEM;

    - ret = simple_write_to_buffer(buf, size, offp, ubuf, size);
    - if (ret < 0) {
    + if (copy_from_user(buf, ubuf, size)) {
    kfree(buf);
    - return ret;
    + return -EFAULT;
    }

    buf[size] = 0;

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