linux-hardening - Coverity: iopt_map_user_pages(): Null pointer dereferences

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Date:   Wed, 2 Nov 2022 12:57:05 -0700
From:   coverity-bot <keescook@...omium.org>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Jason Gunthorpe <jgg@...dia.com>,
        Nicolin Chen <nicolinc@...dia.com>,
        Yi Liu <yi.l.liu@...el.com>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        linux-next@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Coverity: iopt_map_user_pages(): Null pointer dereferences

Hello!

This is an experimental semi-automated report about issues detected by
Coverity from a scan of next-20221102 as part of the linux-next scan project:
https://scan.coverity.com/projects/linux-next-weekly-scan

You're getting this email because you were associated with the identified
lines of code (noted below) that were touched by commits:

  Mon Oct 31 13:37:57 2022 -0300
    91b4be750274 ("iommufd: Data structure to provide IOVA to PFN mapping")

Coverity reported the following:

*** CID 1527090:  Null pointer dereferences  (REVERSE_INULL)
/drivers/iommu/iommufd/io_pagetable.c: 417 in iopt_map_user_pages()
411     	list_add(&elm.next, &pages_list);
412
413     	rc = iopt_map_pages(iopt, &pages_list, length, iova, iommu_prot, flags);
414     	if (rc) {
415     		if (elm.area)
416     			iopt_abort_area(elm.area);
vvv     CID 1527090:  Null pointer dereferences  (REVERSE_INULL)
vvv     Null-checking "elm.pages" suggests that it may be null, but it has already been dereferenced on all paths leading to the check.
417     		if (elm.pages)
418     			iopt_put_pages(elm.pages);
419     		return rc;
420     	}
421     	return 0;
422     }

If this is a false positive, please let us know so we can mark it as
such, or teach the Coverity rules to be smarter. If not, please make
sure fixes get into linux-next. :) For patches fixing this, please
include these lines (but double-check the "Fixes" first):

Reported-by: coverity-bot <keescook+coverity-bot@...omium.org>
Addresses-Coverity-ID: 1527090 ("Null pointer dereferences")
Fixes: 91b4be750274 ("iommufd: Data structure to provide IOVA to PFN mapping")

This looks like the earlier "if (IS_ERR(elm.pages))" should use
IS_ERR_OR_NULL() ?

Thanks for your attention!

-- 
Coverity-bot