diff mbox series

[5.4,110/309] erofs: fix out-of-bound read for shifted uncompressed block

Message ID 20200210122417.201476227@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman Feb. 10, 2020, 12:31 p.m. UTC 
From: Gao Xiang <gaoxiang25@huawei.com>

commit 4d2024370d877f9ac8b98694bcff666da6a5d333 upstream.

rq->out[1] should be valid before accessing. Otherwise,
in very rare cases, out-of-bound dirty onstack rq->out[1]
can equal to *in and lead to unintended memmove behavior.

Link: https://lore.kernel.org/r/20200107022546.19432-1-gaoxiang25@huawei.com
Fixes: 7fc45dbc938a ("staging: erofs: introduce generic decompression backend")
Cc: <stable@vger.kernel.org> # 5.3+
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/erofs/decompressor.c |   22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)
diff mbox series

Patch

--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -306,24 +306,22 @@  static int z_erofs_shifted_transform(con
 	}
 
 	src = kmap_atomic(*rq->in);
-	if (!rq->out[0]) {
-		dst = NULL;
-	} else {
+	if (rq->out[0]) {
 		dst = kmap_atomic(rq->out[0]);
 		memcpy(dst + rq->pageofs_out, src, righthalf);
+		kunmap_atomic(dst);
 	}
 
-	if (rq->out[1] == *rq->in) {
-		memmove(src, src + righthalf, rq->pageofs_out);
-	} else if (nrpages_out == 2) {
-		if (dst)
-			kunmap_atomic(dst);
+	if (nrpages_out == 2) {
 		DBG_BUGON(!rq->out[1]);
-		dst = kmap_atomic(rq->out[1]);
-		memcpy(dst, src + righthalf, rq->pageofs_out);
+		if (rq->out[1] == *rq->in) {
+			memmove(src, src + righthalf, rq->pageofs_out);
+		} else {
+			dst = kmap_atomic(rq->out[1]);
+			memcpy(dst, src + righthalf, rq->pageofs_out);
+			kunmap_atomic(dst);
+		}
 	}
-	if (dst)
-		kunmap_atomic(dst);
 	kunmap_atomic(src);
 	return 0;
 }