From: Jason Gunthorpe <jgg@nvidia.com>
To: coverity-bot <keescook@chromium.org>
Cc: Nicolin Chen <nicolinc@nvidia.com>, Yi Liu <yi.l.liu@intel.com>,
"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
linux-next@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: Coverity: iopt_map_user_pages(): Null pointer dereferences
Date: Wed, 2 Nov 2022 17:14:04 -0300 [thread overview]
Message-ID: <Y2LPjFFkYk0mW+bo@nvidia.com> (raw)
In-Reply-To: <202211021256.2F571DFD@keescook>
On Wed, Nov 02, 2022 at 12:57:05PM -0700, coverity-bot wrote:
> 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@chromium.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() ?
No, that exits the function, can't get to this code with a NULL or ERR
from iopt_alloc_pages()
It becomes NULL because one of the things iopt_map_pages() is to make
it NULL.
I think it is complaining that on the rc!=0 path of iopt_map_pages()
it never makes it NULL.
But I think I will leave this alone as the protocol to destroy an elm
is to do all these tests, and an open coded stack creation of a elm
shouldn't be asymetric with the heap allocated elms.
Thanks,
Jason
prev parent reply other threads:[~2022-11-02 20:14 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-02 19:57 Coverity: iopt_map_user_pages(): Null pointer dereferences coverity-bot
2022-11-02 20:14 ` Jason Gunthorpe [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Y2LPjFFkYk0mW+bo@nvidia.com \
--to=jgg@nvidia.com \
--cc=gustavo@embeddedor.com \
--cc=keescook@chromium.org \
--cc=linux-hardening@vger.kernel.org \
--cc=linux-next@vger.kernel.org \
--cc=nicolinc@nvidia.com \
--cc=yi.l.liu@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).