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erofs: fix out-of-bound access when z_erofs_gbuf_growsize() partially fails

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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: syzbot+242ee56aaa9585553766@syzkaller.appspotmail.com
Fixes: d6db47e571 ("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>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240820085619.1375963-1-hsiangkao@linux.alibaba.com
This commit is contained in:
Gao Xiang 2024-08-20 16:56:19 +08:00
parent e080a26725
commit 0005e01e1e
1 changed files with 2 additions and 1 deletions
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3
fs/erofs/zutil.c
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@ -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);
}