From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:43287) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ti6hF-0003hT-8l for qemu-devel@nongnu.org; Mon, 10 Dec 2012 11:59:24 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ti6h9-0002v0-1K for qemu-devel@nongnu.org; Mon, 10 Dec 2012 11:59:13 -0500 Received: from e28smtp09.in.ibm.com ([122.248.162.9]:51959) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ti6h8-0002uq-8W for qemu-devel@nongnu.org; Mon, 10 Dec 2012 11:59:06 -0500 Received: from /spool/local by e28smtp09.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 10 Dec 2012 22:28:49 +0530 Received: from d28relay05.in.ibm.com (d28relay05.in.ibm.com [9.184.220.62]) by d28dlp02.in.ibm.com (Postfix) with ESMTP id 52888394004C for ; Mon, 10 Dec 2012 22:29:00 +0530 (IST) Received: from d28av04.in.ibm.com (d28av04.in.ibm.com [9.184.220.66]) by d28relay05.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id qBAGwwUs19398746 for ; Mon, 10 Dec 2012 22:28:59 +0530 Received: from d28av04.in.ibm.com (loopback [127.0.0.1]) by d28av04.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id qBAGwxM7007432 for ; Tue, 11 Dec 2012 03:58:59 +1100 From: Anthony Liguori In-Reply-To: <87d2yoe9q2.fsf@linux.vnet.ibm.com> References: <87d2yoe9q2.fsf@linux.vnet.ibm.com> Date: Mon, 10 Dec 2012 10:58:53 -0600 Message-ID: <87ip89269e.fsf@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: Re: [Qemu-devel] [PULL] VirtFS update List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Aneesh Kumar K.V" Cc: QEMU Developers "Aneesh Kumar K.V" writes: > The following changes since commit 16c6c80ac3a772b42a87b77dfdf0fdac7c607b0e: > > Open up 1.4 development branch (2012-12-03 14:08:40 -0600) > > are available in the git repository at: > > git://github.com/kvaneesh/qemu.git for-upstream > > for you to fetch changes up to 9fd2ecdc8cb2dc1a8a7c57b6c9c60bc9947b6a73: > > virtfs-proxy-helper: use setresuid and setresgid (2012-12-05 21:55:54 +0530) > Pulled. Thanks. Regards, Anthony Liguori > ---------------------------------------------------------------- > Paolo Bonzini (1): > virtfs-proxy-helper: use setresuid and setresgid > > fsdev/virtfs-proxy-helper.c | 93 +++++++++++++++++++++++++++++-------------- > 1 file changed, 64 insertions(+), 29 deletions(-) > > diff --git a/fsdev/virtfs-proxy-helper.c b/fsdev/virtfs-proxy-helper.c > index f9a8270..df2a939 100644 > --- a/fsdev/virtfs-proxy-helper.c > +++ b/fsdev/virtfs-proxy-helper.c > @@ -272,31 +272,76 @@ static int send_status(int sockfd, struct iovec *iovec, int status) > /* > * from man 7 capabilities, section > * Effect of User ID Changes on Capabilities: > - * 4. If the file system user ID is changed from 0 to nonzero (see setfsuid(2)) > - * then the following capabilities are cleared from the effective set: > - * CAP_CHOWN, CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH, CAP_FOWNER, CAP_FSETID, > - * CAP_LINUX_IMMUTABLE (since Linux 2.2.30), CAP_MAC_OVERRIDE, and CAP_MKNOD > - * (since Linux 2.2.30). If the file system UID is changed from nonzero to 0, > - * then any of these capabilities that are enabled in the permitted set > - * are enabled in the effective set. > + * If the effective user ID is changed from nonzero to 0, then the permitted > + * set is copied to the effective set. If the effective user ID is changed > + * from 0 to nonzero, then all capabilities are are cleared from the effective > + * set. > + * > + * The setfsuid/setfsgid man pages warn that changing the effective user ID may > + * expose the program to unwanted signals, but this is not true anymore: for an > + * unprivileged (without CAP_KILL) program to send a signal, the real or > + * effective user ID of the sending process must equal the real or saved user > + * ID of the target process. Even when dropping privileges, it is enough to > + * keep the saved UID to a "privileged" value and virtfs-proxy-helper won't > + * be exposed to signals. So just use setresuid/setresgid. > */ > -static int setfsugid(int uid, int gid) > +static int setugid(int uid, int gid, int *suid, int *sgid) > { > + int retval; > + > /* > - * We still need DAC_OVERRIDE because we don't change > + * We still need DAC_OVERRIDE because we don't change > * supplementary group ids, and hence may be subjected DAC rules > */ > cap_value_t cap_list[] = { > CAP_DAC_OVERRIDE, > }; > > - setfsgid(gid); > - setfsuid(uid); > + *suid = geteuid(); > + *sgid = getegid(); > + > + if (setresgid(-1, gid, *sgid) == -1) { > + retval = -errno; > + goto err_out; > + } > + > + if (setresuid(-1, uid, *suid) == -1) { > + retval = -errno; > + goto err_sgid; > + } > > if (uid != 0 || gid != 0) { > - return do_cap_set(cap_list, ARRAY_SIZE(cap_list), 0); > + if (do_cap_set(cap_list, ARRAY_SIZE(cap_list), 0) < 0) { > + retval = -errno; > + goto err_suid; > + } > } > return 0; > + > +err_suid: > + if (setresuid(-1, *suid, *suid) == -1) { > + abort(); > + } > +err_sgid: > + if (setresgid(-1, *sgid, *sgid) == -1) { > + abort(); > + } > +err_out: > + return retval; > +} > + > +/* > + * This is used to reset the ugid back with the saved values > + * There is nothing much we can do checking error values here. > + */ > +static void resetugid(int suid, int sgid) > +{ > + if (setresgid(-1, sgid, sgid) == -1) { > + abort(); > + } > + if (setresuid(-1, suid, suid) == -1) { > + abort(); > + } > } > > /* > @@ -578,18 +623,15 @@ static int do_create_others(int type, struct iovec *iovec) > > v9fs_string_init(&path); > v9fs_string_init(&oldpath); > - cur_uid = geteuid(); > - cur_gid = getegid(); > > retval = proxy_unmarshal(iovec, offset, "dd", &uid, &gid); > if (retval < 0) { > return retval; > } > offset += retval; > - retval = setfsugid(uid, gid); > + retval = setugid(uid, gid, &cur_uid, &cur_gid); > if (retval < 0) { > - retval = -errno; > - goto err_out; > + goto unmarshal_err_out; > } > switch (type) { > case T_MKNOD: > @@ -619,9 +661,10 @@ static int do_create_others(int type, struct iovec *iovec) > } > > err_out: > + resetugid(cur_uid, cur_gid); > +unmarshal_err_out: > v9fs_string_free(&path); > v9fs_string_free(&oldpath); > - setfsugid(cur_uid, cur_gid); > return retval; > } > > @@ -641,24 +684,16 @@ static int do_create(struct iovec *iovec) > if (ret < 0) { > goto unmarshal_err_out; > } > - cur_uid = geteuid(); > - cur_gid = getegid(); > - ret = setfsugid(uid, gid); > + ret = setugid(uid, gid, &cur_uid, &cur_gid); > if (ret < 0) { > - /* > - * On failure reset back to the > - * old uid/gid > - */ > - ret = -errno; > - goto err_out; > + goto unmarshal_err_out; > } > ret = open(path.data, flags, mode); > if (ret < 0) { > ret = -errno; > } > > -err_out: > - setfsugid(cur_uid, cur_gid); > + resetugid(cur_uid, cur_gid); > unmarshal_err_out: > v9fs_string_free(&path); > return ret;