mail archive of the barebox mailing list
 help / color / mirror / Atom feed
From: Stefan Kerkmann <s.kerkmann@pengutronix.de>
To: Sascha Hauer <s.hauer@pengutronix.de>,
	 BAREBOX <barebox@lists.infradead.org>
Cc: Stefan Kerkmann <s.kerkmann@pengutronix.de>
Subject: [PATCH 2/2] of: fdt: fix oob writes with large ftd properties
Date: Wed, 31 Jan 2024 17:57:00 +0100	[thread overview]
Message-ID: <20240131-fix-fdt-memory-safety-v1-2-3d3a2c797eec@pengutronix.de> (raw)
In-Reply-To: <20240131-fix-fdt-memory-safety-v1-0-3d3a2c797eec@pengutronix.de>

OOB writes can be triggered when fdt->dt_size * 2 is still smaller than
the property for which memory should be allocated. This can happen under
rare circumstances when editing a fdt with the of_property command and a
property is larger than 128k in size.

This happend when editing a FIT image (which is a ftd) with the
of_property command and the Kernel image was around 8M in size.

The simplified call chain is the following:

of_property -> of_flatten_dtb -> create new fdt with 64k in size (this is
fixed) -> __of_flatten_dtb -> attempt to copy kernel image (8M) ->
fdt_ensure_space -> allocate only 128k for fdt->dt -> memcopy 8M into fdt->dt
buffer -> crash

The fix is to grow fdt->dt to hold at least the new property. The power
of 2 increment is untouched to keep the same behaviour otherwise.

Signed-off-by: Stefan Kerkmann <s.kerkmann@pengutronix.de>
---
 drivers/of/fdt.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 4f79a6120f..1f24ed0bbc 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -399,6 +399,10 @@ static int fdt_ensure_space(struct fdt *fdt, int dtsize)
 		previous = fdt->dt;
 		new_size = fdt->dt_size * 2;
 
+		while (new_size <= dtsize) {
+			new_size *= 2;
+		}
+
 		if ((fdt->dt = memalign_realloc(previous, fdt->dt_size,
 						new_size)) == NULL) {
 			free(previous);

-- 
2.39.2




  parent reply	other threads:[~2024-01-31 16:57 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-01-31 16:56 [PATCH 0/2] of: fdt: fix memory leak and oob writes in fdt_ensure_space Stefan Kerkmann
2024-01-31 16:56 ` [PATCH 1/2] of: fdt: fix memory leak " Stefan Kerkmann
2024-01-31 17:15   ` Ahmad Fatoum
2024-02-01  8:34     ` Stefan Kerkmann
2024-01-31 16:57 ` Stefan Kerkmann [this message]
2024-01-31 17:21   ` [PATCH 2/2] of: fdt: fix oob writes with large ftd properties Ahmad Fatoum
2024-02-01 10:24     ` Stefan Kerkmann
2024-02-01 10:42       ` Ahmad Fatoum
2024-02-01  7:47   ` Sascha Hauer
2024-02-01  8:49     ` Stefan Kerkmann

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20240131-fix-fdt-memory-safety-v1-2-3d3a2c797eec@pengutronix.de \
    --to=s.kerkmann@pengutronix.de \
    --cc=barebox@lists.infradead.org \
    --cc=s.hauer@pengutronix.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox