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FAILED: patch "[PATCH] ubifs: wbuf: Don't leak kernel memory to flash" failed to apply to 4.9-stable tree

PATCH [email protected] 1 participant 1 message Dec 28, 2020

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Stable branch UBI file system (UBIFS)
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The patch below does not apply to the 4.9-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 <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 20f1431160c6b590cdc269a846fc5a448abf5b98 Mon Sep 17 00:00:00 2001
From: Richard Weinberger <[email protected]>
Date: Mon, 16 Nov 2020 22:05:30 +0100
Subject: [PATCH] ubifs: wbuf: Don't leak kernel memory to flash

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 <[email protected]>
Fixes 1e51764a3c2ac05a2 ("UBIFS: add new flash file system")
Signed-off-by Richard Weinberger <[email protected]>
Reviewed-by Zhihao Cheng <[email protected]>
Signed-off-by Richard Weinberger <[email protected]>
fs/ubifs/io.c +11 -2
index 2dc933f73165..a9cabb3fa64c 100644
@@ -319,7 +319,7 @@ void ubifs_pad(const struct ubifs_info *c, void *buf, int pad)
 {
 	uint32_t crc;
 
-	ubifs_assert(c, pad >= 0 && !(pad & 7));
+	ubifs_assert(c, pad >= 0);
 
 	if (pad >= UBIFS_PAD_NODE_SZ) {
 		struct ubifs_ch *ch = buf;

@@ -764,6 +764,10 @@ 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(c, 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",

@@ -856,13 +860,18 @@ 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(c, 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;