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Message-Id: <20200210122436.153487613@linuxfoundation.org>
Date: Mon, 10 Feb 2020 04:30:36 -0800
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Chao Yu <yuchao0@...wei.com>,
Gao Xiang <gaoxiang25@...wei.com>
Subject: [PATCH 5.5 123/367] erofs: fix out-of-bound read for shifted uncompressed block
From: Gao Xiang <gaoxiang25@...wei.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@...r.kernel.org> # 5.3+
Reviewed-by: Chao Yu <yuchao0@...wei.com>
Signed-off-by: Gao Xiang <gaoxiang25@...wei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
fs/erofs/decompressor.c | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)
--- 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;
}
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