From 37b5d72da2e736aab333b984fc42e27d707db02d Mon Sep 17 00:00:00 2001
From: Gao Xiang <hsiangkao@linux.alibaba.com>
Date: Tue, 20 Aug 2024 16:56:19 +0800
Subject: [PATCH] UPSTREAM: erofs: fix out-of-bound access when
 z_erofs_gbuf_growsize() partially fails

If z_erofs_gbuf_growsize() partially fails on a global buffer due to
memory allocation failure or fault injection (as reported by syzbot [1]),
new pages need to be freed by comparing to the existing pages to avoid
memory leaks.

However, the old gbuf->pages[] array may not be large enough, which can
lead to null-ptr-deref or out-of-bound access.

Fix this by checking against gbuf->nrpages in advance.

[1] https://lore.kernel.org/r/000000000000f7b96e062018c6e3@google.com

Bug: 361158066
Reported-by: syzbot+242ee56aaa9585553766@syzkaller.appspotmail.com
Fixes: d6db47e571dc ("erofs: do not use pagepool in z_erofs_gbuf_growsize()")
Cc: <stable@vger.kernel.org> # 6.10+
Reviewed-by: Chunhai Guo <guochunhai@vivo.com>
Reviewed-by: Sandeep Dhavale <dhavale@google.com>
Change-Id: If63b4f4ba19a9f83efa8c8e24ad6e6e215ca8186
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240820085619.1375963-1-hsiangkao@linux.alibaba.com
(cherry picked from commit 0005e01e1e875c5e27130c5e2ed0189749d1e08a)