Hi Greg,
On Mon, Dec 28, 2020 at 10:30:49AM +0100, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
>
> The patch below does not apply to the 4.14-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
Here is the backport, will also apply to 4.9-stable and 4.4-stable.
--
Regards
Sudip
>From b37cba57bea48fba2de82b9def75167730cefb3b Mon Sep 17 00:00:00 2001
From: Richard Weinberger <richard@xxxxxx>
Date: Mon, 16 Nov 2020 22:05:30 +0100
Subject: [PATCH] ubifs: wbuf: Don't leak kernel memory to flash
commit 20f1431160c6b590cdc269a846fc5a448abf5b98 upstream
Write buffers use a kmalloc()'ed buffer, they can leak
up to seven bytes of kernel memory to flash if writes are not
aligned.
So use ubifs_pad() to fill these gaps with padding bytes.
This was never a problem while scanning because the scanner logic
manually aligns node lengths and skips over these gaps.
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 1e51764a3c2ac05a2 ("UBIFS: add new flash file system")
Signed-off-by: Richard Weinberger <richard@xxxxxx>
Reviewed-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
Signed-off-by: Richard Weinberger <richard@xxxxxx>
[sudip: adjust context]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx>
---
fs/ubifs/io.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/fs/ubifs/io.c b/fs/ubifs/io.c
index 135e95950f51..5b4d4b1087c4 100644
--- a/fs/ubifs/io.c
+++ b/fs/ubifs/io.c
@@ -331,7 +331,7 @@ void ubifs_pad(const struct ubifs_info *c, void *buf, int pad)
{
uint32_t crc;
- ubifs_assert(pad >= 0 && !(pad & 7));
+ ubifs_assert(pad >= 0);
if (pad >= UBIFS_PAD_NODE_SZ) {
struct ubifs_ch *ch = buf;
@@ -727,6 +727,10 @@ int ubifs_wbuf_write_nolock(struct ubifs_wbuf *wbuf, void *buf, int len)
* write-buffer.
*/
memcpy(wbuf->buf + wbuf->used, buf, len);
+ if (aligned_len > len) {
+ ubifs_assert(aligned_len - len < 8);
+ ubifs_pad(c, wbuf->buf + wbuf->used + len, aligned_len - len);
+ }
if (aligned_len == wbuf->avail) {
dbg_io("flush jhead %s wbuf to LEB %d:%d",
@@ -819,13 +823,18 @@ int ubifs_wbuf_write_nolock(struct ubifs_wbuf *wbuf, void *buf, int len)
}
spin_lock(&wbuf->lock);
- if (aligned_len)
+ if (aligned_len) {
/*
* And now we have what's left and what does not take whole
* max. write unit, so write it to the write-buffer and we are
* done.
*/
memcpy(wbuf->buf, buf + written, len);
+ if (aligned_len > len) {
+ ubifs_assert(aligned_len - len < 8);
+ ubifs_pad(c, wbuf->buf + len, aligned_len - len);
+ }
+ }
if (c->leb_size - wbuf->offs >= c->max_write_size)
wbuf->size = c->max_write_size;
--
2.11.0
