[PATCH] bootstd: android: Fix write outside of memory

[Chris Morgan]

On Tue, Jan 06, 2026 at 11:16:33AM -0600, Tom Rini wrote:
> On Tue, Dec 23, 2025 at 05:44:56PM -0600, Chris Morgan wrote:
> 
> > From: Chris Morgan <macromorgan at hotmail.com>
> > 
> > It looks like under certain circumstances when reading the vendor_boot
> > partition it causes my device to write outside the range of memory
> > available. Near as I can tell this occurs because
> > scan_vendor_boot_part() calls android_image_get_vendor_bootimg_size()
> > which calls android_vendor_boot_image_v3_v4_parse_hdr() which calls
> > add_trailer() which attempts to copy information to a buffer allocated
> > with malloc in the scan_vendor_boot_part() function. On my board the
> > memory set aside for malloc is at the top of the system RAM, and given
> > a large enough vendor boot image size this causes the write from
> > add_trailer() to occur outside of the system RAM (nevermind outside
> > of what was allocated with the malloc().
> > 
> > While I don't know the absolute best way to handle this, I would assume
> > that if we simply map the memory we want to use to where we will
> > eventually load the vendor_boot image that would be the most logical.
> > 
> > Fixes: abadcda24b10 ("bootstd: android: don't read whole partition sizes")
> > Signed-off-by: Chris Morgan <macromorgan at hotmail.com>
> > ---
> >  boot/bootmeth_android.c | 20 ++++++--------------
> >  1 file changed, 6 insertions(+), 14 deletions(-)
> > 
> > diff --git a/boot/bootmeth_android.c b/boot/bootmeth_android.c
> > index 1374551dbeb..c2c25d53ef3 100644
> > --- a/boot/bootmeth_android.c
> > +++ b/boot/bootmeth_android.c
> > @@ -118,9 +118,10 @@ static int scan_vendor_boot_part(struct udevice *blk, struct android_priv *priv)
> >  	struct blk_desc *desc = dev_get_uclass_plat(blk);
> >  	struct disk_partition partition;
> >  	char partname[PART_NAME_LEN];
> > -	ulong num_blks, bufsz;
> > +	ulong num_blks;
> >  	char *buf;
> >  	int ret;
> > +	ulong vloadaddr = env_get_hex("vendor_boot_comp_addr_r", 0);
> >  
> >  	if (priv->slot)
> >  		sprintf(partname, VENDOR_BOOT_PART_NAME "_%s", priv->slot);
> > @@ -132,28 +133,19 @@ static int scan_vendor_boot_part(struct udevice *blk, struct android_priv *priv)
> >  		return log_msg_ret("part info", ret);
> >  
> >  	num_blks = DIV_ROUND_UP(sizeof(struct andr_vnd_boot_img_hdr), desc->blksz);
> > -	bufsz = num_blks * desc->blksz;
> > -	buf = malloc(bufsz);
> > +	buf = map_sysmem(vloadaddr, 0);
> >  	if (!buf)
> >  		return log_msg_ret("buf", -ENOMEM);
> >  
> >  	ret = blk_read(blk, partition.start, num_blks, buf);
> > -	if (ret != num_blks) {
> > -		free(buf);
> > +	if (ret != num_blks)
> >  		return log_msg_ret("part read", -EIO);
> > -	}
> >  
> > -	if (!is_android_vendor_boot_image_header(buf)) {
> > -		free(buf);
> > +	if (!is_android_vendor_boot_image_header(buf))
> >  		return log_msg_ret("header", -ENOENT);
> > -	}
> >  
> > -	if (!android_image_get_vendor_bootimg_size(buf, &priv->vendor_boot_img_size)) {
> > -		free(buf);
> > +	if (!android_image_get_vendor_bootimg_size(buf, &priv->vendor_boot_img_size))
> >  		return log_msg_ret("get vendor bootimg size", -EINVAL);
> > -	}
> > -
> > -	free(buf);
> >  
> >  	return 0;
> >  }
> 
> I haven't forgotten about this, but I'm hoping there's some other way to
> solve this, I'm not super keen on adding another environment variable
> (that would need to be documented in a v2 if we can't fix this some
> other way). Mattijs, do you have any ideas?
> 

Would using hdr->ramdisk_addr as the end address in
android_vendor_boot_image_v3_v4_parse_hdr() work instead of (ulong)hdr?

That of course assumes the ram disk isn't manually loaded elsewhere.

Thank you,
Chris

> -- 
> Tom