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mm/gup: fix memfd_pin_folios alloc race panic

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If memfd_pin_folios tries to create a hugetlb page, but someone else
already did, then folio gets the value -EEXIST here:

        folio = memfd_alloc_folio(memfd, start_idx);
        if (IS_ERR(folio)) {
                ret = PTR_ERR(folio);
                if (ret != -EEXIST)
                        goto err;

then on the next trip through the "while start_idx" loop we panic here:

        if (folio) {
                folio_put(folio);

To fix, set the folio to NULL on error.

Link: https://lkml.kernel.org/r/1725373521-451395-6-git-send-email-steven.sistare@oracle.com
Fixes: 89c1905d9c ("mm/gup: introduce memfd_pin_folios() for pinning memfd folios")
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Acked-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Steve Sistare 2024-09-03 07:25:21 -07:00 committed by Andrew Morton
parent 9289f020da
commit ce645b9fdc
1 changed files with 1 additions and 0 deletions
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mm/gup.c
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@ -3702,6 +3702,7 @@ long memfd_pin_folios(struct file *memfd, loff_t start, loff_t end,
ret = PTR_ERR(folio);
if (ret != -EEXIST)
goto err;
folio = NULL;
}
}
}