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bh=+e7SqpyZGiTrfR3lUQklNbqi4pTd3BmIJ0/CVHKgypE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=CwmncR1kjliO9eTCZUICtnvkbDgebhr9QKeBjXAjLYTrM0RoU1hemb79pqnLIVFQU yy1d8xTomcuMKXr3qRmUsDRGrkPJAAY5YIUFvu2VsShGZsiYSZsCIV1h4zK+vz64Xj VxQyZvEC0YROFPIXpcvAJaQQE3QPYnIWS0lO9Tg8= Date: Tue, 4 Apr 2023 14:17:22 -0700 From: Andrew Morton To: "xiaosong.ma" Cc: , , Zhaoyang Huang , Subject: Re: [PATCH] mm: check mapping addr is correct when dump page Message-Id: <20230404141722.45dbdc377e7e1547e302ffa5@linux-foundation.org> In-Reply-To: <1680587425-4683-1-git-send-email-Xiaosong.Ma@unisoc.com> References: <1680587425-4683-1-git-send-email-Xiaosong.Ma@unisoc.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 4577C10001C X-Rspam-User: X-Stat-Signature: jqz4x4gnj7bnijanuaet4nnez9bsghe3 X-HE-Tag: 1680643046-501221 X-HE-Meta: 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 VDfzAsgp bP5Am1jgIYYV75AQou8bW8OmrY3UR+5dG813qX9c0/NDe7anb/JtcZhPjqOi3gmcilBsubxI4KK07ATZqulfGFw25DoUVqGJxXMo35xg5cajExfRGgaC/czjB015Z5hXihNIf2KFV8lvMmyVGMdHIpAGyOFWRtQO7IxFRJs3+fqZivqXocdDl27k+M6fbY8C8G53Sx+cGYPrgoUx+7FNBvKeaGekase6QibH/JAyfBw9GtExeIwFAU7Jm8RNPfgDbsQpe7daXpvVEwC54A5A5TYq2bAx9GV6D+vX/V4W7ShIYtr7sXfzM/wECXIgAn4ebe8QNMZ7eWS6LfMrrqfByERTZNbAauL481riiN73urONMwgzHGi3VW3OHoo97U2nyiSs2OLptLzUMOK5nAqWfedZYMA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, 4 Apr 2023 13:50:25 +0800 "xiaosong.ma" wrote: > when we debug with slub_debug_on, the following backtraces show dump_page > will show wrong info when the bad page is non-NULL mapping and page->mapping > is 0x80000000000 so do virt_addr valid check is needed when dump mapping page. How did this page get ->mapping=0x80000000? I don't recall anywhere where we deliberately set this state. Maybe a random bitscribble? I guess being defensive in __dump_page() is sensible - we have reason to believe that the page is in some bad state. > --- a/mm/debug.c > +++ b/mm/debug.c > @@ -109,7 +109,7 @@ static void __dump_page(struct page *page) > type = "ksm "; > else if (PageAnon(page)) > type = "anon "; > - else if (mapping) > + else if (mapping && virt_addr_valid(mapping)) > dump_mapping(mapping); I expect the user will be interested in knowing that ->mapping contains junk, so perhaps we should print some information telling them this. In which case, dump_mapping() would be a better place to perform the check. And lo, dump_mapping() already did this, so I think all we need is --- a/fs/inode.c~a +++ a/fs/inode.c @@ -565,7 +565,8 @@ void dump_mapping(const struct address_s * If mapping is an invalid pointer, we don't want to crash * accessing it, so probe everything depending on it carefully. */ - if (get_kernel_nofault(host, &mapping->host) || + if (get_kernel_nofault(mapping) || + get_kernel_nofault(host, &mapping->host) || get_kernel_nofault(a_ops, &mapping->a_ops)) { pr_warn("invalid mapping:%px\n", mapping); return; _