Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752822Ab3CREsS (ORCPT ); Mon, 18 Mar 2013 00:48:18 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:33445 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751645Ab3CREaT (ORCPT ); Mon, 18 Mar 2013 00:30:19 -0400 Message-Id: <20130318042150.936654279@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Mon, 18 Mar 2013 04:22:53 +0000 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, Mathieu Desnoyers , Linus Torvalds , Al Viro Subject: [ 69/82] Fix: compat_rw_copy_check_uvector() misuse in aio, readv, writev, and security keys In-Reply-To: <20130318042144.234468645@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:d98f:da4e:f620:7bea X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4245 Lines: 133 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mathieu Desnoyers commit 8aec0f5d4137532de14e6554fd5dd201ff3a3c49 upstream. Looking at mm/process_vm_access.c:process_vm_rw() and comparing it to compat_process_vm_rw() shows that the compatibility code requires an explicit "access_ok()" check before calling compat_rw_copy_check_uvector(). The same difference seems to appear when we compare fs/read_write.c:do_readv_writev() to fs/compat.c:compat_do_readv_writev(). This subtle difference between the compat and non-compat requirements should probably be debated, as it seems to be error-prone. In fact, there are two others sites that use this function in the Linux kernel, and they both seem to get it wrong: Now shifting our attention to fs/aio.c, we see that aio_setup_iocb() also ends up calling compat_rw_copy_check_uvector() through aio_setup_vectored_rw(). Unfortunately, the access_ok() check appears to be missing. Same situation for security/keys/compat.c:compat_keyctl_instantiate_key_iov(). I propose that we add the access_ok() check directly into compat_rw_copy_check_uvector(), so callers don't have to worry about it, and it therefore makes the compat call code similar to its non-compat counterpart. Place the access_ok() check in the same location where copy_from_user() can trigger a -EFAULT error in the non-compat code, so the ABI behaviors are alike on both compat and non-compat. While we are here, fix compat_do_readv_writev() so it checks for compat_rw_copy_check_uvector() negative return values. And also, fix a memory leak in compat_keyctl_instantiate_key_iov() error handling. Acked-by: Linus Torvalds Acked-by: Al Viro Signed-off-by: Mathieu Desnoyers Signed-off-by: Linus Torvalds [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- fs/compat.c | 15 +++++++-------- mm/process_vm_access.c | 8 -------- security/keys/compat.c | 4 ++-- 3 files changed, 9 insertions(+), 18 deletions(-) --- a/fs/compat.c +++ b/fs/compat.c @@ -572,6 +572,10 @@ ssize_t compat_rw_copy_check_uvector(int } *ret_pointer = iov; + ret = -EFAULT; + if (!access_ok(VERIFY_READ, uvector, nr_segs*sizeof(*uvector))) + goto out; + /* * Single unix specification: * We should -EINVAL if an element length is not >= 0 and fitting an @@ -1103,17 +1107,12 @@ static ssize_t compat_do_readv_writev(in if (!file->f_op) goto out; - ret = -EFAULT; - if (!access_ok(VERIFY_READ, uvector, nr_segs*sizeof(*uvector))) - goto out; - - tot_len = compat_rw_copy_check_uvector(type, uvector, nr_segs, + ret = compat_rw_copy_check_uvector(type, uvector, nr_segs, UIO_FASTIOV, iovstack, &iov, 1); - if (tot_len == 0) { - ret = 0; + if (ret <= 0) goto out; - } + tot_len = ret; ret = rw_verify_area(type, file, pos, tot_len); if (ret < 0) goto out; --- a/mm/process_vm_access.c +++ b/mm/process_vm_access.c @@ -434,12 +434,6 @@ compat_process_vm_rw(compat_pid_t pid, if (flags != 0) return -EINVAL; - if (!access_ok(VERIFY_READ, lvec, liovcnt * sizeof(*lvec))) - goto out; - - if (!access_ok(VERIFY_READ, rvec, riovcnt * sizeof(*rvec))) - goto out; - if (vm_write) rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV, iovstack_l, @@ -464,8 +458,6 @@ free_iovecs: kfree(iov_r); if (iov_l != iovstack_l) kfree(iov_l); - -out: return rc; } --- a/security/keys/compat.c +++ b/security/keys/compat.c @@ -40,12 +40,12 @@ long compat_keyctl_instantiate_key_iov( ARRAY_SIZE(iovstack), iovstack, &iov, 1); if (ret < 0) - return ret; + goto err; if (ret == 0) goto no_payload_free; ret = keyctl_instantiate_key_common(id, iov, ioc, ret, ringid); - +err: if (iov != iovstack) kfree(iov); return ret; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/