From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Sun, 26 Apr 2015 11:47:44 +0000 (+0200)
Subject: 4.0-stable patches
X-Git-Tag: v4.0.1~4
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b56e170415b29c4de3f270c291ede02c759a5915;p=thirdparty%2Fkernel%2Fstable-queue.git

4.0-stable patches

added patches:
	fs-take-i_mutex-during-prepare_binprm-for-setid-executables.patch
---

diff --git a/queue-4.0/fs-take-i_mutex-during-prepare_binprm-for-setid-executables.patch b/queue-4.0/fs-take-i_mutex-during-prepare_binprm-for-setid-executables.patch
new file mode 100644
index 00000000000..99b54b4bd0e
--- /dev/null
+++ b/queue-4.0/fs-take-i_mutex-during-prepare_binprm-for-setid-executables.patch
@@ -0,0 +1,117 @@
+From 8b01fc86b9f425899f8a3a8fc1c47d73c2c20543 Mon Sep 17 00:00:00 2001
+From: Jann Horn <jann@thejh.net>
+Date: Sun, 19 Apr 2015 02:48:39 +0200
+Subject: fs: take i_mutex during prepare_binprm for set[ug]id executables
+
+From: Jann Horn <jann@thejh.net>
+
+commit 8b01fc86b9f425899f8a3a8fc1c47d73c2c20543 upstream.
+
+This prevents a race between chown() and execve(), where chowning a
+setuid-user binary to root would momentarily make the binary setuid
+root.
+
+This patch was mostly written by Linus Torvalds.
+
+Signed-off-by: Jann Horn <jann@thejh.net>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ fs/exec.c |   76 +++++++++++++++++++++++++++++++++++++++-----------------------
+ 1 file changed, 48 insertions(+), 28 deletions(-)
+
+--- a/fs/exec.c
++++ b/fs/exec.c
+@@ -1265,6 +1265,53 @@ static void check_unsafe_exec(struct lin
+ 	spin_unlock(&p->fs->lock);
+ }
+ 
++static void bprm_fill_uid(struct linux_binprm *bprm)
++{
++	struct inode *inode;
++	unsigned int mode;
++	kuid_t uid;
++	kgid_t gid;
++
++	/* clear any previous set[ug]id data from a previous binary */
++	bprm->cred->euid = current_euid();
++	bprm->cred->egid = current_egid();
++
++	if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
++		return;
++
++	if (task_no_new_privs(current))
++		return;
++
++	inode = file_inode(bprm->file);
++	mode = READ_ONCE(inode->i_mode);
++	if (!(mode & (S_ISUID|S_ISGID)))
++		return;
++
++	/* Be careful if suid/sgid is set */
++	mutex_lock(&inode->i_mutex);
++
++	/* reload atomically mode/uid/gid now that lock held */
++	mode = inode->i_mode;
++	uid = inode->i_uid;
++	gid = inode->i_gid;
++	mutex_unlock(&inode->i_mutex);
++
++	/* We ignore suid/sgid if there are no mappings for them in the ns */
++	if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
++		 !kgid_has_mapping(bprm->cred->user_ns, gid))
++		return;
++
++	if (mode & S_ISUID) {
++		bprm->per_clear |= PER_CLEAR_ON_SETID;
++		bprm->cred->euid = uid;
++	}
++
++	if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
++		bprm->per_clear |= PER_CLEAR_ON_SETID;
++		bprm->cred->egid = gid;
++	}
++}
++
+ /*
+  * Fill the binprm structure from the inode.
+  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
+@@ -1273,36 +1320,9 @@ static void check_unsafe_exec(struct lin
+  */
+ int prepare_binprm(struct linux_binprm *bprm)
+ {
+-	struct inode *inode = file_inode(bprm->file);
+-	umode_t mode = inode->i_mode;
+ 	int retval;
+ 
+-
+-	/* clear any previous set[ug]id data from a previous binary */
+-	bprm->cred->euid = current_euid();
+-	bprm->cred->egid = current_egid();
+-
+-	if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) &&
+-	    !task_no_new_privs(current) &&
+-	    kuid_has_mapping(bprm->cred->user_ns, inode->i_uid) &&
+-	    kgid_has_mapping(bprm->cred->user_ns, inode->i_gid)) {
+-		/* Set-uid? */
+-		if (mode & S_ISUID) {
+-			bprm->per_clear |= PER_CLEAR_ON_SETID;
+-			bprm->cred->euid = inode->i_uid;
+-		}
+-
+-		/* Set-gid? */
+-		/*
+-		 * If setgid is set but no group execute bit then this
+-		 * is a candidate for mandatory locking, not a setgid
+-		 * executable.
+-		 */
+-		if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
+-			bprm->per_clear |= PER_CLEAR_ON_SETID;
+-			bprm->cred->egid = inode->i_gid;
+-		}
+-	}
++	bprm_fill_uid(bprm);
+ 
+ 	/* fill in binprm security blob */
+ 	retval = security_bprm_set_creds(bprm);
diff --git a/queue-4.0/series b/queue-4.0/series
index f63af7def87..baf81b212d9 100644
--- a/queue-4.0/series
+++ b/queue-4.0/series
@@ -4,3 +4,4 @@ bnx2x-fix-busy_poll-vs-netpoll.patch
 bpf-fix-verifier-memory-corruption.patch
 revert-net-reset-secmark-when-scrubbing-packet.patch
 skbuff-do-not-scrub-skb-mark-within-the-same-name-space.patch
+fs-take-i_mutex-during-prepare_binprm-for-setid-executables.patch