Commit 0005e01e authored by Gao Xiang's avatar Gao Xiang
Browse files

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



Reported-by: default avatar <syzbot+242ee56aaa9585553766@syzkaller.appspotmail.com>
Fixes: d6db47e5 ("erofs: do not use pagepool in z_erofs_gbuf_growsize()")
Cc: <stable@vger.kernel.org> # 6.10+
Reviewed-by: default avatarChunhai Guo <guochunhai@vivo.com>
Reviewed-by: default avatarSandeep Dhavale <dhavale@google.com>
Signed-off-by: default avatarGao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240820085619.1375963-1-hsiangkao@linux.alibaba.com
parent e080a267

fs/erofs/zutil.c

+2 −1
Original line number Diff line number Diff line
@@ -111,7 +111,8 @@ int z_erofs_gbuf_growsize(unsigned int nrpages) 
out:

	if (i < z_erofs_gbuf_count && tmp_pages) {

		for (j = 0; j < nrpages; ++j)

			if (tmp_pages[j] && tmp_pages[j] != gbuf->pages[j])

			if (tmp_pages[j] && (j >= gbuf->nrpages ||

					     tmp_pages[j] != gbuf->pages[j]))

				__free_page(tmp_pages[j]);

		kfree(tmp_pages);

	}