Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [PATCH] mm/folio-compact: fix potential NULL pointer in pagecache_get_page | From | Yongqiang Liu <> | Date | Thu, 28 Jul 2022 09:36:48 +0800 |
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Understood, thanks for your explanation :)
在 2022/7/27 19:40, William Kucharski 写道: > This isn't a NULL pointer dereference; returning &(0->page) is completely legal > as was discussed regarding this exact code back in April: > > https://lore.kernel.org/lkml/YmfgqKcMmstgfz+0@casper.infradead.org/ > >> On Jul 27, 2022, at 12:46 AM, Yongqiang Liu <liuyongqiang13@huawei.com> wrote: >> >> When __filemap_get_folio() failed and returned NULL, we would >> get a NULL pointer dereference in pagecache_get_page. >> >> Fixes: 3f0c6a07fee6 ("mm/filemap: Add filemap_get_folio") >> Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com> >> Cc: <stable@vger.kernel.org> # 5.16 >> --- >> mm/folio-compat.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/mm/folio-compat.c b/mm/folio-compat.c >> index 20bc15b57d93..7b21393480e0 100644 >> --- a/mm/folio-compat.c >> +++ b/mm/folio-compat.c >> @@ -124,7 +124,9 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index, >> struct folio *folio; >> >> folio = __filemap_get_folio(mapping, index, fgp_flags, gfp); >> - if ((fgp_flags & FGP_HEAD) || !folio || xa_is_value(folio)) >> + if (!folio) >> + return NULL; >> + if ((fgp_flags & FGP_HEAD) || xa_is_value(folio)) >> return &folio->page; >> return folio_file_page(folio, index); >> } >> -- >> 2.25.1 >> >> > .
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