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=1794585549; b=WHyCGtcaA5k+WO+DRlMJZpaS4F0zxKDOfwgc694P4sKTIgKDuqUSCxYaW53VCQs3vf3B pofI5R3IZEAoPdoCNJLriR1eDkWOcWaeb+eoPVV96OLOLSLuUu7Sj7vfrwP9xbmGTCWWC 854gJCj/gPmwkSkSQPGTQGmXeC5PSCcuGb5tRZu9yW9AHe7pMMyvrzRgQCqjyk+10KeLq DNwaL2CHgcspGhI+mUwnM5p7ZTDdRdesBjvRRZ9Zgtko2EYgBFTos59lpkfkdZJgKRDtJ N12Vg8MeYhhMJWSKyG3DJzxKjG64BV38akBzFRGkkJnTKiwevdLPHEKI3fdjw6HY9DA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794585549; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=QBz9kYnBgbyFkLVqoU7/+Y4gMiBcnIdblenJJf/Ywp4=; b=j5U0GRqspBK8mETSPOlILClRsRXhw14cXIQ4cQGk6gg1XDpQGrn8bHwNSX8nv/SFUaWj weRAwF2LZAR1fMRJOeeNz/j6xy9H0fdfAQjTisp1mnTTpV9Se9AONSwH4a42ULc7uL1te VMdOHkzr9jw4qIb2anRlBKfcDGp/ATxPVpYb5FhRNQuVCWhtsONCw4hzsWXP/s5boXvj3 Mf7bGKEYHc0O/C+A1juxNEQyN/lIrlqa2IMMbDLthhg3Ss5j3dmHN8wVYpcU1AKq9u1BY 3zGVlUcpc7Fs4U/0bs60tYxhrkpBk7PxurWESgXNsNiLkATVPq1hhmpbHjvAkdf8MAA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=EFvVumLO; 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 84D0D606BA80; Fri, 13 Nov 2026 15:59:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=EFvVumLO Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3327F1F000C4; Fri, 13 Nov 2026 15:59:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794585549; bh=QBz9kYnBgbyFkLVqoU7/+Y4gMiBcnIdblenJJf/Ywp4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=EFvVumLOwujnCUpLeisYerRKGjRhTvpgQLoHqBxVwjvw3WvBDGR/OfWA2/Wv7aJuI 8Z6uCvJD0xk44fbye5wPZgDPK/IhmbuvCZCSNF4ILilkLHh+TUEOUOm4HgcJfzshhr ZClA/PqsTsdRSOWp7eIA156OM52zY8kQYKFg7wYo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Josef Bacik , "Lorenzo Stoakes (ARM)" , Rik van Riel , "Vlastimil Babka (SUSE)" , Barry Song , Pedro Falcato , "Harry Yoo (Meta)" , "Kiryl Shutsemau (Meta)" , SJ Park , Muhammad Usama Anjum , "David Hildenbrand (Arm)" , Sasha Levin Subject: [PATCH 7.3 146/507] fork: take mmap_lock before copying mm_struct Date: Fri, 13 Nov 2026 10:47:30 -0500 Message-ID: <20261113153759.379801734@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153753.358973689@linuxfoundation.org> References: <20261113153753.358973689@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore 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 7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Hildenbrand (Arm) [ Upstream commit ef694e2d210111cc08c52fd25da9ab130170bfa3 ] dup_mm() copies the parent's mm_struct before dup_mmap() takes the mmap_lock. A concurrent brk() can leave the child with a stale mm->brk and newer heap mappings, causing later brk() requests to fail. Other operations (e.g., PR_SET_MM) on the parent's mm_struct can similarly cause inconsistencies. As a simple and robust fix, grab the parent's mmap_lock earlier. This way we don't need to update individual mm fields in dup_mmap() and keep missing ones. Stop updating the 4 existing members (total_vm, data_vm, exec_vm, stack_vm), as that is now no longer required. Keep releasing the parent's mmap_lock in dup_mmap(), before userfaultfd completion, to avoid moving the userfaultfd handling into the caller. This should get cleaned up later. Move uprobe_start_dup_mmap() to preserve the lock ordering. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Reported-by: Josef Bacik Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Rik van Riel Reviewed-by: Vlastimil Babka (SUSE) Reviewed-by: Barry Song Reviewed-by: Pedro Falcato Reviewed-by: Harry Yoo (Meta) Reviewed-by: Kiryl Shutsemau (Meta) Reviewed-by: SJ Park Tested-by: Muhammad Usama Anjum Link: https://patch.msgid.link/20261031-fixes_core-v3-2-d6437171ecc3@kernel.org Signed-off-by: David Hildenbrand (Arm) Signed-off-by: Sasha Levin --- kernel/fork.c | 20 ++++++++++++++------ mm/mmap.c | 8 +------- mm/nommu.c | 2 +- 3 files changed, 16 insertions(+), 14 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index 8ad34646962d2..48d7ca0644042 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1535,12 +1535,19 @@ static struct mm_struct *dup_mm(struct task_struct *tsk, if (!mm) goto fail_nomem; + uprobe_start_dup_mmap(); + if (mmap_write_lock_killable(oldmm)) { + free_mm(mm); + goto fail_uprobe; + } + memcpy(mm, oldmm, sizeof(*mm)); - if (!mm_init(mm, tsk)) - goto fail_nomem; + if (!mm_init(mm, tsk)) { + mmap_write_unlock(oldmm); + goto fail_uprobe; + } - uprobe_start_dup_mmap(); err = dup_mmap(mm, oldmm); if (err) goto free_pt; @@ -1559,9 +1566,10 @@ static struct mm_struct *dup_mm(struct task_struct *tsk, mm->binfmt = NULL; mm_init_owner(mm, NULL); mmput(mm); - if (err) - uprobe_end_dup_mmap(); - + if (!err) + return NULL; +fail_uprobe: + uprobe_end_dup_mmap(); fail_nomem: return NULL; } diff --git a/mm/mmap.c b/mm/mmap.c index 4bf26b0f1e6e3..6f22cd76be4f3 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1713,8 +1713,7 @@ __latent_entropy int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) LIST_HEAD(uf); VMA_ITERATOR(vmi, mm, 0); - if (mmap_write_lock_killable(oldmm)) - return -EINTR; + mmap_assert_write_locked(oldmm); flush_cache_dup_mm(oldmm); uprobe_dup_mmap(oldmm, mm); /* @@ -1725,11 +1724,6 @@ __latent_entropy int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) /* No ordering required: file already has been exposed. */ dup_mm_exe_file(mm, oldmm); - mm->total_vm = oldmm->total_vm; - mm->data_vm = oldmm->data_vm; - mm->exec_vm = oldmm->exec_vm; - mm->stack_vm = oldmm->stack_vm; - /* Use __mt_dup() to efficiently build an identical maple tree. */ retval = __mt_dup(&oldmm->mm_mt, &mm->mm_mt, GFP_KERNEL); if (unlikely(retval)) diff --git a/mm/nommu.c b/mm/nommu.c index ed44510e37707..6e0f9c7da2364 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1926,7 +1926,7 @@ subsys_initcall(init_admin_reserve); int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) { - mmap_write_lock(oldmm); + mmap_assert_write_locked(oldmm); dup_mm_exe_file(mm, oldmm); mmap_write_unlock(oldmm); return 0; -- 2.53.0