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authorJohn Hubbard <jhubbard@nvidia.com>2024-11-20 19:49:33 -0800
committerAndrew Morton <akpm@linux-foundation.org>2024-12-05 19:54:42 -0800
commita1268be280d8e484ab3606d7476edd0f14bb9961 (patch)
tree1571036e81abb3057c6ac6a35b2229f078341aa0 /mm
parentdef13795928b82ecca4ae3ea16f375114ff88685 (diff)
mm/gup: handle NULL pages in unpin_user_pages()
The recent addition of "pofs" (pages or folios) handling to gup has a flaw: it assumes that unpin_user_pages() handles NULL pages in the pages** array. That's not the case, as I discovered when I ran on a new configuration on my test machine. Fix this by skipping NULL pages in unpin_user_pages(), just like unpin_folios() already does. Details: when booting on x86 with "numa=fake=2 movablecore=4G" on Linux 6.12, and running this: tools/testing/selftests/mm/gup_longterm ...I get the following crash: BUG: kernel NULL pointer dereference, address: 0000000000000008 RIP: 0010:sanity_check_pinned_pages+0x3a/0x2d0 ... Call Trace: <TASK> ? __die_body+0x66/0xb0 ? page_fault_oops+0x30c/0x3b0 ? do_user_addr_fault+0x6c3/0x720 ? irqentry_enter+0x34/0x60 ? exc_page_fault+0x68/0x100 ? asm_exc_page_fault+0x22/0x30 ? sanity_check_pinned_pages+0x3a/0x2d0 unpin_user_pages+0x24/0xe0 check_and_migrate_movable_pages_or_folios+0x455/0x4b0 __gup_longterm_locked+0x3bf/0x820 ? mmap_read_lock_killable+0x12/0x50 ? __pfx_mmap_read_lock_killable+0x10/0x10 pin_user_pages+0x66/0xa0 gup_test_ioctl+0x358/0xb20 __se_sys_ioctl+0x6b/0xc0 do_syscall_64+0x7b/0x150 entry_SYSCALL_64_after_hwframe+0x76/0x7e Link: https://lkml.kernel.org/r/20241121034933.77502-1-jhubbard@nvidia.com Fixes: 94efde1d1539 ("mm/gup: avoid an unnecessary allocation call for FOLL_LONGTERM cases") Signed-off-by: John Hubbard <jhubbard@nvidia.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vivek Kasireddy <vivek.kasireddy@intel.com> Cc: Dave Airlie <airlied@redhat.com> Cc: Gerd Hoffmann <kraxel@redhat.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Peter Xu <peterx@redhat.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Dongwon Kim <dongwon.kim@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Junxiao Chang <junxiao.chang@intel.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/gup.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/mm/gup.c b/mm/gup.c
index 746070a1d8bf..3b75e631f369 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -52,7 +52,12 @@ static inline void sanity_check_pinned_pages(struct page **pages,
*/
for (; npages; npages--, pages++) {
struct page *page = *pages;
- struct folio *folio = page_folio(page);
+ struct folio *folio;
+
+ if (!page)
+ continue;
+
+ folio = page_folio(page);
if (is_zero_page(page) ||
!folio_test_anon(folio))
@@ -409,6 +414,10 @@ void unpin_user_pages(struct page **pages, unsigned long npages)
sanity_check_pinned_pages(pages, npages);
for (i = 0; i < npages; i += nr) {
+ if (!pages[i]) {
+ nr = 1;
+ continue;
+ }
folio = gup_folio_next(pages, npages, i, &nr);
gup_put_folio(folio, nr, FOLL_PIN);
}