Merge branch 'linux-3.18.y' of git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable into linux-linaro-lsk-v3.18lsk-v3.18-15.05

* 'linux-3.18.y' of git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable: (222 commits)
  Linux 3.18.14
  Drivers: hv: vmbus: Don't wait after requesting offers
  hfsplus: don't store special "osx" xattr prefix on-disk
  drm/radeon: check new address before removing old one
  drm/radeon: add SI DPM quirk for Sapphire R9 270 Dual-X 2G GDDR5
  drm/radeon: adjust pll when audio is not enabled
  3w-sas: fix command completion race
  3w-9xxx: fix command completion race
  3w-xxxx: fix command completion race
  ext4: move check under lock scope to close a race.
  ext4: fix data corruption caused by unwritten and delayed extents
  uas: Set max_sectors_240 quirk for ASM1053 devices
  uas: Add US_FL_MAX_SECTORS_240 flag
  uas: Allow uas_use_uas_driver to return usb-storage flags
  rbd: end I/O the entire obj_request on error
  tty/serial: at91: maxburst was missing for dma transfers
  ACPI / SBS: Enable battery manager when present
  btrfs: unlock i_mutex after attempting to delete subvolume during send
  ASoC: rt5677: fixed wrong DMIC ref clock
  ASoC: dapm: Enable autodisable on SOC_DAPM_SINGLE_TLV_AUTODISABLE
  ...

1 files changed, 48 insertions, 28 deletions

diff --git a/fs/exec.c b/fs/exec.c
index 7302b75a9820..2e83209016ec 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1250,6 +1250,53 @@ static void check_unsafe_exec(struct linux_binprm *bprm)
 	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
@@ -1258,36 +1305,9 @@ static void check_unsafe_exec(struct linux_binprm *bprm)
  */
 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);