ad1ebbe5cea8 - main - loader: create local copy of mode list provided by vbeinfoblock

[Ravi Pokala]

Hi Toomas,

-----Original Message-----
From: <owner-src-committers at freebsd.org> on behalf of Toomas Soome <tsoome at FreeBSD.org>
Date: 2021-01-16, Saturday at 00:23
To: <src-committers at FreeBSD.org>, <dev-commits-src-all at FreeBSD.org>, <dev-commits-src-main at FreeBSD.org>
Subject: git: ad1ebbe5cea8 - main - loader: create local copy of mode list provided by vbeinfoblock

    The branch main has been updated by tsoome:

    URL: https://cgit.FreeBSD.org/src/commit/?id=ad1ebbe5cea8ffac0037966990ddf0f80faa55d5

    commit ad1ebbe5cea8ffac0037966990ddf0f80faa55d5
    Author:     Toomas Soome <tsoome at FreeBSD.org>
    AuthorDate: 2021-01-16 10:18:32 +0000
    Commit:     Toomas Soome <tsoome at FreeBSD.org>
    CommitDate: 2021-01-16 10:23:22 +0000

        loader: create local copy of mode list provided by vbeinfoblock

        Apparently some systems do corrupt mode list memory area, so we need
        to use local copy instead.

...

    +	vbe_mode_list_size = (uintptr_t)p - (uintptr_t)ml;
    +	vbe_mode_list = malloc(vbe_mode_list_size);
    +	if (vbe_mode_list == NULL) {
    +		free(vbe);
    +		vbe = NULL;
    +		free(vbe_mode);
    +		vbe_mode = NULL;
    +	}
    +	bcopy(ml, vbe_mode_list, vbe_mode_list_size);
    +
    +	/* reset VideoModePtr, so we will not have chance to use bad data. */
    +	vbe->VideoModePtr = 0;

If allocation of vbe_mode_list failed, you're freeing things that were allocated before it, but then you're continuing on. The very next thing you do is the bcopy(), which dereferences vbe_mode_list, which is NULL because of the allocation failure.

That doesn't seem right.

Thanks,

Ravi (rpokala@)