From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0CB18522D for ; Sun, 9 Jul 2023 11:14:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7722EC433C7; Sun, 9 Jul 2023 11:14:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1688901272; bh=ANrfaKyJP2FUXOaM31vYzQIlBUTQnUVpURxMjTlfYhE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=J2TmXLKxMcupYV3st+JR8Q3VPaGif2WpTk23nqO7CSlR0L6p6nHtk3k2nhPJyBM9x J4PH9KAXO4tz3ZxATlniessi/uDG1m9Kqa+P6T82T/CdGGkC5DRc2uuxljuWoS2kRD jN+PeYQeIpH1j2pCxEK/ANV4U6XqdKQqSVgPonMs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Suren Baghdasaryan , Linus Torvalds Subject: [PATCH 6.4 3/8] mm: lock newly mapped VMA which can be modified after it becomes visible Date: Sun, 9 Jul 2023 13:14:09 +0200 Message-ID: <20230709111345.397858220@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230709111345.297026264@linuxfoundation.org> References: <20230709111345.297026264@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Suren Baghdasaryan commit 33313a747e81af9f31d0d45de78c9397fa3655eb upstream. mmap_region adds a newly created VMA into VMA tree and might modify it afterwards before dropping the mmap_lock. This poses a problem for page faults handled under per-VMA locks because they don't take the mmap_lock and can stumble on this VMA while it's still being modified. Currently this does not pose a problem since post-addition modifications are done only for file-backed VMAs, which are not handled under per-VMA lock. However, once support for handling file-backed page faults with per-VMA locks is added, this will become a race. Fix this by write-locking the VMA before inserting it into the VMA tree. Other places where a new VMA is added into VMA tree do not modify it after the insertion, so do not need the same locking. Cc: stable@vger.kernel.org Signed-off-by: Suren Baghdasaryan Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/mmap.c | 2 ++ 1 file changed, 2 insertions(+) --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2804,6 +2804,8 @@ cannot_expand: if (vma->vm_file) i_mmap_lock_write(vma->vm_file->f_mapping); + /* Lock the VMA since it is modified after insertion into VMA tree */ + vma_start_write(vma); vma_iter_store(&vmi, vma); mm->map_count++; if (vma->vm_file) {