Commit 111767c1 authored by Thomas Cedeno's avatar Thomas Cedeno Committed by Micah Morton
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LSM: Signal to SafeSetID when setting group IDs 



For SafeSetID to properly gate set*gid() calls, it needs to know whether
ns_capable() is being called from within a sys_set*gid() function or is
being called from elsewhere in the kernel. This allows SafeSetID to deny
CAP_SETGID to restricted groups when they are attempting to use the
capability for code paths other than updating GIDs (e.g. setting up
userns GID mappings). This is the identical approach to what is
currently done for CAP_SETUID.

NOTE: We also add signaling to SafeSetID from the setgroups() syscall,
as we have future plans to restrict a process' ability to set
supplementary groups in addition to what is added in this series for
restricting setting of the primary group.

Signed-off-by: default avatarThomas Cedeno <thomascedeno@google.com>
Signed-off-by: default avatarMicah Morton <mortonm@chromium.org>
parent bbf5c979

kernel/capability.c

+1 −1
Original line number Diff line number Diff line
@@ -418,7 +418,7 @@ EXPORT_SYMBOL(ns_capable_noaudit); 
/**

 * ns_capable_setid - Determine if the current task has a superior capability

 * in effect, while signalling that this check is being done from within a

 * setid syscall.

 * setid or setgroups syscall.

 * @ns:  The usernamespace we want the capability in

 * @cap: The capability to be tested for

 *

kernel/groups.c

+1 −1
Original line number Diff line number Diff line
@@ -178,7 +178,7 @@ bool may_setgroups(void) 
{

	struct user_namespace *user_ns = current_user_ns();



	return ns_capable(user_ns, CAP_SETGID) &&

	return ns_capable_setid(user_ns, CAP_SETGID) &&

		userns_may_setgroups(user_ns);

}

kernel/sys.c

+5 −5
Original line number Diff line number Diff line
@@ -373,7 +373,7 @@ long __sys_setregid(gid_t rgid, gid_t egid) 
	if (rgid != (gid_t) -1) {

		if (gid_eq(old->gid, krgid) ||

		    gid_eq(old->egid, krgid) ||

		    ns_capable(old->user_ns, CAP_SETGID))

		    ns_capable_setid(old->user_ns, CAP_SETGID))

			new->gid = krgid;

		else

			goto error;
@@ -382,7 +382,7 @@ long __sys_setregid(gid_t rgid, gid_t egid) 
		if (gid_eq(old->gid, kegid) ||

		    gid_eq(old->egid, kegid) ||

		    gid_eq(old->sgid, kegid) ||

		    ns_capable(old->user_ns, CAP_SETGID))

		    ns_capable_setid(old->user_ns, CAP_SETGID))

			new->egid = kegid;

		else

			goto error;
@@ -432,7 +432,7 @@ long __sys_setgid(gid_t gid) 
	old = current_cred();



	retval = -EPERM;

	if (ns_capable(old->user_ns, CAP_SETGID))

	if (ns_capable_setid(old->user_ns, CAP_SETGID))

		new->gid = new->egid = new->sgid = new->fsgid = kgid;

	else if (gid_eq(kgid, old->gid) || gid_eq(kgid, old->sgid))

		new->egid = new->fsgid = kgid;
@@ -744,7 +744,7 @@ long __sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid) 
	old = current_cred();



	retval = -EPERM;

	if (!ns_capable(old->user_ns, CAP_SETGID)) {

	if (!ns_capable_setid(old->user_ns, CAP_SETGID)) {

		if (rgid != (gid_t) -1        && !gid_eq(krgid, old->gid) &&

		    !gid_eq(krgid, old->egid) && !gid_eq(krgid, old->sgid))

			goto error;
@@ -871,7 +871,7 @@ long __sys_setfsgid(gid_t gid) 


	if (gid_eq(kgid, old->gid)  || gid_eq(kgid, old->egid)  ||

	    gid_eq(kgid, old->sgid) || gid_eq(kgid, old->fsgid) ||

	    ns_capable(old->user_ns, CAP_SETGID)) {

	    ns_capable_setid(old->user_ns, CAP_SETGID)) {

		if (!gid_eq(kgid, old->fsgid)) {

			new->fsgid = kgid;

			if (security_task_fix_setgid(new,old,LSM_SETID_FS) == 0)

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