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CVE-2015-3339 race condition between chown and execve (rhbz 1214030)

This commit is contained in:
Josh Boyer 2015-04-24 12:44:51 -04:00
parent 9df1e847d8
commit b3135c06b1
2 changed files with 123 additions and 0 deletions
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116
fs-take-i_mutex-during-prepare_binprm-for-set-ug-id-.patch Normal file
View File

@ -0,0 +1,116 @@
From: Jann Horn <jann@thejh.net>
Date: Sun, 19 Apr 2015 02:48:39 +0200
Subject: [PATCH] fs: take i_mutex during prepare_binprm for set[ug]id
executables
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>
---
fs/exec.c | 76 ++++++++++++++++++++++++++++++++++++++++-----------------------
1 file changed, 48 insertions(+), 28 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index ad8798e26be9..4617a4ec52e3 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1259,6 +1259,53 @@ 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
@@ -1267,36 +1314,9 @@ 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);
--
2.1.0

7
kernel.spec
View File

@ -667,6 +667,9 @@ Patch26181: 0001-iwlwifi-mvm-remove-WARN_ON-for-invalid-BA-notificati.patch
#rhbz 1208999
Patch26182: SCSI-add-1024-max-sectors-black-list-flag.patch
#CVE-2015-3330 rbhz 1214030
Patch26188: fs-take-i_mutex-during-prepare_binprm-for-set-ug-id-.patch
# END OF PATCH DEFINITIONS
%endif
@ -1442,6 +1445,9 @@ ApplyPatch 0001-iwlwifi-mvm-remove-WARN_ON-for-invalid-BA-notificati.patch
#rhbz 1208999
ApplyPatch SCSI-add-1024-max-sectors-black-list-flag.patch
#CVE-2015-3330 rbhz 1214030
ApplyPatch fs-take-i_mutex-during-prepare_binprm-for-set-ug-id-.patch
# END OF PATCH APPLICATIONS
%endif
@ -2302,6 +2308,7 @@ fi
# || ||
%changelog
* Fri Apr 24 2015 Josh Boyer <jwboyer@fedoraproject.org>
- CVE-2015-3339 race condition between chown and execve (rhbz 1214030)
- Fix iscsi with QNAP devices (rhbz 1208999)
* Thu Apr 23 2015 Laura Abbott <labbott@fedoraproject.com>