From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794439088; b=i8Vx+TTodbfGh5/VamDxtE16xdV3UT0j2jjwPRfUT57e7dPPhq2js4N2gwpvGJz2h8uY zgXKGFWg8IJ4Gh2dSv+1s9fLc/O9pISDV0pNDUI+rGCXBrz8haJic5YKaOoDi18FP0x7u miO4zlrbBKnOS2fHSgPZ418oXbG3BwbLRCWzhHwmI1LCHF7Pj9P6bARsdjlwhSY6BfMDK c0bwvexAr3dxh4x7oJYlEemEzPynkyBBoefqWwKrxZdkPNqUXnwzxONYOO8xXNn/Ro3uK 1CedgfO3wZLkoePStjRiRjP3nngps9t8HLBV8K53tJ8qKcV9gHiCYN6Zcs8lWLQ/NIg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794439088; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=Ix0kB5hn1z7nvbCxmDdqbXSje3Q9X95mpbUUgO1whQQ=; b=a8usDYT6Kn71UIpvLxruegLiRHMrUC2kvONvdrjJhkEj24psEIfiILQ/Jxq7qHjUXThl krvCpmKMaVl7bBfl19dbNRn7JK05+wM/XeYlPd+JnRKeYafzBJ3SrzYVZN+MXLWMGTSJy Rv0a6GJ82ZafwRbMsXLVOqXa/Z2QSZCH2jR+yoccIXzWUVREygw65Sv/u6xE9a23uwTsp wqjVWn0EKZUUe93AJui52udgiN+QC1t/WP5i7n05SStuL3J6u1MCVt1Mi0bgdfMaHYA9b UJhUnlFdU1QhJRGJopYm4HtyJBcZdE8L0ElvpScxTpKNRMHH6yKl1YFFsayUBK1DCGQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Ob7OB7Th; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 04191606A321 for ; Wed, 11 Nov 2026 23:18:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Ob7OB7Th Received: by smtp.kernel.org (Postfix) with ESMTPSA id C1CB31F00A05; Wed, 11 Nov 2026 23:18:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794439087; bh=Ix0kB5hn1z7nvbCxmDdqbXSje3Q9X95mpbUUgO1whQQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Ob7OB7ThmIEWF83rHuCEENvNfdrNsisrf77Uh8Z+9g5DXfr0bRyGqAbbIswakxHB7 ERv4DeYHGLgJv6TTDCE6kCuxsUHjoJkt4JBNblvVconhcZJzOIDv0E5X61WHzRr9wn cPcfQG19ExPn/l6HU4LpzI7l8PMHeLxzFICcL6Sq0FWf/R8DESWBN1nJMSgXCvkZL5 gTI9iXhXmlWX6a9ylmvOkbv6Bn6xrsYsVLhCtTKNWbPc80nG8pzE0iQXVNR6v50gAb EgpAkerPO1XvjfTsQhPwvTYGrnSrlYPg6tVLBWbmqHKVqmCoG2S3rFiCfXRHkFZkPx g1QA0X4fkqdgw== From: Sasha Levin To: stable@vger.kernel.org Cc: "David Hildenbrand (Arm)" , "Gregory Price (Meta)" , "Mike Rapoport (Microsoft)" , "Lorenzo Stoakes (ARM)" , Muhammad Usama Anjum , Sasha Levin Subject: [PATCH 6.12.y] mm/userfaultfd: wake waiters when registration modes are removed Date: Wed, 11 Nov 2026 18:18:05 -0500 Message-ID: <20261111231749.463731-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109200903-failed-6.12-4eee9c389b07@kernel.org> References: <20261109200903-failed-6.12-4eee9c389b07@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "David Hildenbrand (Arm)" [ Upstream commit 4eee9c389b072e161549d46dcb1ae10b0222717e ] UFFDIO_REGISTER can replace MISSING or MINOR tracking without waking faults that are already queued. For example, switching an anonymous range from MISSING to WP leaves a missing-fault waiter asleep until userspace explicitly wakes it. When a registration change removes a UFFD mode, wake waiters in the affected interval after updating the VMA. The VMA is write-locked at this point, so no new faults can queue under the old modes and woken threads cannot retry until mmap_write_unlock(). Waiters for retained modes in the same interval may also wake and refault. The hang reproduces for MISSING-to-WP and MINOR-to-MISSING transitions, with both read and unread fault events. Fixes: 63b2d4174c4a ("userfaultfd: wp: add the writeprotect API to userfaultfd ioctl") Cc: stable@vger.kernel.org Reviewed-by: Gregory Price (Meta) Tested-by: Gregory Price (Meta) Signed-off-by: Gregory Price (Meta) Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: Lorenzo Stoakes (ARM) Tested-by: Muhammad Usama Anjum Link: https://patch.msgid.link/20261031-fixes_core-v3-25-d6437171ecc3@kernel.org Signed-off-by: David Hildenbrand (Arm) [ sashal: replaced the local wake_userfault_range() wrapper with a direct wake_userfault() call, exposing the helper and its range structure across files ] Signed-off-by: Sasha Levin --- fs/userfaultfd.c | 9 ++------- include/linux/userfaultfd_k.h | 8 ++++++++ mm/userfaultfd.c | 12 ++++++++++++ 3 files changed, 22 insertions(+), 7 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index cbd9d610c54bf..71084cf5b7989 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -71,11 +71,6 @@ struct userfaultfd_wait_queue { bool waken; }; -struct userfaultfd_wake_range { - unsigned long start; - unsigned long len; -}; - /* internal indication that UFFD_API ioctl was successfully executed */ #define UFFD_FEATURE_INITIALIZED (1u << 31) @@ -1185,8 +1180,8 @@ static void __wake_userfault(struct userfaultfd_ctx *ctx, spin_unlock_irq(&ctx->fault_pending_wqh.lock); } -static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, - struct userfaultfd_wake_range *range) +void wake_userfault(struct userfaultfd_ctx *ctx, + struct userfaultfd_wake_range *range) { unsigned seq; bool need_wakeup; diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 8ff68ce1860be..8b8be5fa2eb57 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -82,6 +82,14 @@ struct userfaultfd_ctx { struct mm_struct *mm; }; +struct userfaultfd_wake_range { + unsigned long start; + unsigned long len; +}; + +void wake_userfault(struct userfaultfd_ctx *ctx, + struct userfaultfd_wake_range *range); + extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason); /* A combined operation mode + behavior flags. */ diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 9951b4f42c65a..33abb025750db 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -1962,6 +1962,8 @@ int userfaultfd_register_range(struct userfaultfd_ctx *ctx, prev = vma; for_each_vma_range(vmi, vma, end) { + const bool any_mode_removed = vma->vm_flags & __VM_UFFD_FLAGS & ~vm_flags; + cond_resched(); BUG_ON(!vma_can_userfault(vma, vm_flags, wp_async)); @@ -1996,6 +1998,16 @@ int userfaultfd_register_range(struct userfaultfd_ctx *ctx, */ userfaultfd_set_ctx(vma, ctx, vm_flags); + /* Retry faults for removed modes while the VMA is write-locked. */ + if (any_mode_removed) { + struct userfaultfd_wake_range range = { + .start = start, + .len = vma_end - start, + }; + + wake_userfault(ctx, &range); + } + if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma)) hugetlb_unshare_all_pmds(vma); -- 2.53.0