The patch titled Subject: lib/iov_iter: fix to increase non slab folio refcount has been added to the -mm mm-hotfixes-unstable branch. Its filename is lib-iov_iter-fix-to-increase-non-slab-folio-refcount.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: Sheng Yong shengyong1@xiaomi.com Subject: lib/iov_iter: fix to increase non slab folio refcount Date: Tue, 1 Apr 2025 22:47:12 +0800
When testing EROFS file-backed mount over v9fs on qemu, I encountered a folio UAF issue. The page sanity check reports the following call trace. The root cause is that pages in bvec are coalesced across a folio bounary. The refcount of all non-slab folios should be increased to ensure p9_releas_pages can put them correctly.
BUG: Bad page state in process md5sum pfn:18300 page: refcount:0 mapcount:0 mapping:00000000d5ad8e4e index:0x60 pfn:0x18300 head: order:0 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 aops:z_erofs_aops ino:30b0f dentry name(?):"GoogleExtServicesCn.apk" flags: 0x100000000000041(locked|head|node=0|zone=1) raw: 0100000000000041 dead000000000100 dead000000000122 ffff888014b13bd0 raw: 0000000000000060 0000000000000020 00000000ffffffff 0000000000000000 head: 0100000000000041 dead000000000100 dead000000000122 ffff888014b13bd0 head: 0000000000000060 0000000000000020 00000000ffffffff 0000000000000000 head: 0100000000000000 0000000000000000 ffffffffffffffff 0000000000000000 head: 0000000000000010 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set Call Trace: dump_stack_lvl+0x53/0x70 bad_page+0xd4/0x220 __free_pages_ok+0x76d/0xf30 __folio_put+0x230/0x320 p9_release_pages+0x179/0x1f0 p9_virtio_zc_request+0xa2a/0x1230 p9_client_zc_rpc.constprop.0+0x247/0x700 p9_client_read_once+0x34d/0x810 p9_client_read+0xf3/0x150 v9fs_issue_read+0x111/0x360 netfs_unbuffered_read_iter_locked+0x927/0x1390 netfs_unbuffered_read_iter+0xa2/0xe0 vfs_iocb_iter_read+0x2c7/0x460 erofs_fileio_rq_submit+0x46b/0x5b0 z_erofs_runqueue+0x1203/0x21e0 z_erofs_readahead+0x579/0x8b0 read_pages+0x19f/0xa70 page_cache_ra_order+0x4ad/0xb80 filemap_readahead.isra.0+0xe7/0x150 filemap_get_pages+0x7aa/0x1890 filemap_read+0x320/0xc80 vfs_read+0x6c6/0xa30 ksys_read+0xf9/0x1c0 do_syscall_64+0x9e/0x1a0 entry_SYSCALL_64_after_hwframe+0x71/0x79
Link: https://lkml.kernel.org/r/20250401144712.1377719-1-shengyong1@xiaomi.com Fixes: b9c0e49abfca ("mm: decline to manipulate the refcount on a slab page") Signed-off-by: Sheng Yong shengyong1@xiaomi.com Reviewed-by: Matthew Wilcox (Oracle) willy@infradead.org Acked-by: Vlastimil Babka vbabka@suse.cz Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
lib/iov_iter.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/lib/iov_iter.c~lib-iov_iter-fix-to-increase-non-slab-folio-refcount +++ a/lib/iov_iter.c @@ -1191,7 +1191,7 @@ static ssize_t __iov_iter_get_pages_allo return -ENOMEM; p = *pages; for (int k = 0; k < n; k++) { - struct folio *folio = page_folio(page); + struct folio *folio = page_folio(page + k); p[k] = page + k; if (!folio_test_slab(folio)) folio_get(folio); _
Patches currently in -mm which might be from shengyong1@xiaomi.com are
lib-iov_iter-fix-to-increase-non-slab-folio-refcount.patch