6.12-stable review patch. If anyone has any objections, please let me know.
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From: Wupeng Ma mawupeng1@huawei.com
commit 1bd6406fb5f36c2bb1e96e27d4c3e9f4d09edde4 upstream.
During our test, it is found that a warning can be trigger in try_grab_folio as follow:
------------[ cut here ]------------ WARNING: CPU: 0 PID: 1678 at mm/gup.c:147 try_grab_folio+0x106/0x130 Modules linked in: CPU: 0 UID: 0 PID: 1678 Comm: syz.3.31 Not tainted 6.15.0-rc5 #163 PREEMPT(undef) RIP: 0010:try_grab_folio+0x106/0x130 Call Trace: <TASK> follow_huge_pmd+0x240/0x8e0 follow_pmd_mask.constprop.0.isra.0+0x40b/0x5c0 follow_pud_mask.constprop.0.isra.0+0x14a/0x170 follow_page_mask+0x1c2/0x1f0 __get_user_pages+0x176/0x950 __gup_longterm_locked+0x15b/0x1060 ? gup_fast+0x120/0x1f0 gup_fast_fallback+0x17e/0x230 get_user_pages_fast+0x5f/0x80 vmci_host_unlocked_ioctl+0x21c/0xf80 RIP: 0033:0x54d2cd ---[ end trace 0000000000000000 ]---
Digging into the source, context->notify_page may init by get_user_pages_fast and can be seen in vmci_ctx_unset_notify which will try to put_page. However get_user_pages_fast is not finished here and lead to following try_grab_folio warning. The race condition is shown as follow:
cpu0 cpu1 vmci_host_do_set_notify vmci_host_setup_notify get_user_pages_fast(uva, 1, FOLL_WRITE, &context->notify_page); lockless_pages_from_mm gup_pgd_range gup_huge_pmd // update &context->notify_page vmci_host_do_set_notify vmci_ctx_unset_notify notify_page = context->notify_page; if (notify_page) put_page(notify_page); // page is freed __gup_longterm_locked __get_user_pages follow_trans_huge_pmd try_grab_folio // warn here
To slove this, use local variable page to make notify_page can be seen after finish get_user_pages_fast.
Fixes: a1d88436d53a ("VMCI: Fix two UVA mapping bugs") Cc: stable stable@kernel.org Closes: https://lore.kernel.org/all/e91da589-ad57-3969-d979-879bbd10dddd@huawei.com/ Signed-off-by: Wupeng Ma mawupeng1@huawei.com Link: https://lore.kernel.org/r/20250510033040.901582-1-mawupeng1@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/misc/vmw_vmci/vmci_host.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-)
--- a/drivers/misc/vmw_vmci/vmci_host.c +++ b/drivers/misc/vmw_vmci/vmci_host.c @@ -227,6 +227,7 @@ static int drv_cp_harray_to_user(void __ static int vmci_host_setup_notify(struct vmci_ctx *context, unsigned long uva) { + struct page *page; int retval;
if (context->notify_page) { @@ -243,13 +244,11 @@ static int vmci_host_setup_notify(struct /* * Lock physical page backing a given user VA. */ - retval = get_user_pages_fast(uva, 1, FOLL_WRITE, &context->notify_page); - if (retval != 1) { - context->notify_page = NULL; + retval = get_user_pages_fast(uva, 1, FOLL_WRITE, &page); + if (retval != 1) return VMCI_ERROR_GENERIC; - } - if (context->notify_page == NULL) - return VMCI_ERROR_UNAVAILABLE; + + context->notify_page = page;
/* * Map the locked page and set up notify pointer.