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 cnKjzC/p 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 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: List-Subscribe: List-Unsubscribe: On 16 Jul 2025, at 10:58, Antonio Quartulli wrote: > I just found this issue in the last linux-next Coverity report and it > caught my attention. > I am not familiar with this code, therefore I am sending this patch > as RFC because I am not 100% sure whether this is a false positive or > not. > However, it seems potentially legit to me: > > In __folio_split(), when looping over folios we dereference > `mapping` before ensuring it is non-NULL. > > Following code in the loop body performs such check, thus > suggesting that `mapping` may be NULL and accessing it > without any check may be dangerous. > > Add NULL check before passing it to shmem_mapping(). > > Cc: Zi Yan > Fixes: 00527733d0dc ("mm/huge_memory: add two new (not yet used) functi= ons for folio_split()") > Addresses-Coverity-ID: 1647614 ("FORWARD_NULL") > Signed-off-by: Antonio Quartulli > --- > mm/huge_memory.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 389620c65a5f..d649026db95a 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -3802,7 +3802,7 @@ static int __folio_split(struct folio *folio, uns= igned int new_order, > > /* Some pages can be beyond EOF: drop them from cache */ > if (new_folio->index >=3D end) { > - if (shmem_mapping(mapping)) > + if (mapping && shmem_mapping(mapping)) > nr_shmem_dropped +=3D folio_nr_pages(new_folio); > else if (folio_test_clear_dirty(new_folio)) > folio_account_cleaned( Hi Antonio, Is there a way of preventing Coverity/sparse from checking certain code? This non-NULL mapping issue pops up every time I touch the code. Dan Carpenter reported the issue yesterday and I explained it is no issue= [1]. The same report showed up when I added __split_unmapped_folio() back in February[2] [1] https://lore.kernel.org/oe-kbuild/64b54034-f311-4e7d-b935-c16775dbb64= 2@suswa.mountain/ [2] https://lore.kernel.org/linux-mm/2afe3d59-aca5-40f7-82a3-a6d976fb0f4f= @stanley.mountain/ I wonder how many times I need to explain this, although I appreciate your effort to improve kernel. Best Regards, Yan, Zi