From 5afb4bf9fc62d828647647ec31745083637132e4 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Tue, 24 Jun 2025 14:40:33 +0100 Subject: [PATCH] io_uring/rsrc: fix folio unpinning syzbot complains about an unmapping failure: [ 108.070381][ T14] kernel BUG at mm/gup.c:71! [ 108.070502][ T14] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP [ 108.123672][ T14] Hardware name: QEMU KVM Virtual Machine, BIOS edk2-20250221-8.fc42 02/21/2025 [ 108.127458][ T14] Workqueue: iou_exit io_ring_exit_work [ 108.174205][ T14] Call trace: [ 108.175649][ T14] sanity_check_pinned_pages+0x7cc/0x7d0 (P) [ 108.178138][ T14] unpin_user_page+0x80/0x10c [ 108.180189][ T14] io_release_ubuf+0x84/0xf8 [ 108.182196][ T14] io_free_rsrc_node+0x250/0x57c [ 108.184345][ T14] io_rsrc_data_free+0x148/0x298 [ 108.186493][ T14] io_sqe_buffers_unregister+0x84/0xa0 [ 108.188991][ T14] io_ring_ctx_free+0x48/0x480 [ 108.191057][ T14] io_ring_exit_work+0x764/0x7d8 [ 108.193207][ T14] process_one_work+0x7e8/0x155c [ 108.195431][ T14] worker_thread+0x958/0xed8 [ 108.197561][ T14] kthread+0x5fc/0x75c [ 108.199362][ T14] ret_from_fork+0x10/0x20 We can pin a tail page of a folio, but then io_uring will try to unpin the head page of the folio. While it should be fine in terms of keeping the page actually alive, mm folks say it's wrong and triggers a debug warning. Use unpin_user_folio() instead of unpin_user_page*. Cc: stable@vger.kernel.org Debugged-by: David Hildenbrand Reported-by: syzbot+1d335893772467199ab6@syzkaller.appspotmail.com Closes: https://lkml.kernel.org/r/683f1551.050a0220.55ceb.0017.GAE@google.com Fixes: a8edbb424b139 ("io_uring/rsrc: enable multi-hugepage buffer coalescing") Signed-off-by: Pavel Begunkov Link: https://lore.kernel.org/io-uring/a28b0f87339ac2acf14a645dad1e95bbcbf18acd.1750771718.git.asml.silence@gmail.com/ [axboe: adapt to current tree, massage commit message] Signed-off-by: Jens Axboe --- io_uring/rsrc.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c index d724602697e7..0c09e38784c9 100644 --- a/io_uring/rsrc.c +++ b/io_uring/rsrc.c @@ -112,8 +112,11 @@ static void io_release_ubuf(void *priv) struct io_mapped_ubuf *imu = priv; unsigned int i; - for (i = 0; i < imu->nr_bvecs; i++) - unpin_user_page(imu->bvec[i].bv_page); + for (i = 0; i < imu->nr_bvecs; i++) { + struct folio *folio = page_folio(imu->bvec[i].bv_page); + + unpin_user_folio(folio, 1); + } } static struct io_mapped_ubuf *io_alloc_imu(struct io_ring_ctx *ctx, @@ -840,8 +843,10 @@ static struct io_rsrc_node *io_sqe_buffer_register(struct io_ring_ctx *ctx, if (ret) { if (imu) io_free_imu(ctx, imu); - if (pages) - unpin_user_pages(pages, nr_pages); + if (pages) { + for (i = 0; i < nr_pages; i++) + unpin_user_folio(page_folio(pages[i]), 1); + } io_cache_free(&ctx->node_cache, node); node = ERR_PTR(ret); }