[PATCH 4.4 045/112] ovl: Fix info leak in ovl_lookup_temp()

From	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups	linux.kernel
Subject	[PATCH 4.4 045/112] ovl: Fix info leak in ovl_lookup_temp()
Date	2016-10-26 15:10 +0200
Message-ID	<sww7W-49u-115@gated-at.bofh.it> (permalink)
References	<swvER-3Eq-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Richard Weinberger <richard@nod.at>

commit 6a45b3628ce4dcf7498b39c87d475bab6e2a9b24 upstream.

The function uses the memory address of a struct dentry as unique id.
While the address-based directory entry is only visible to root it is IMHO
still worth fixing since the temporary name does not have to be a kernel
address.  It can be any unique number.  Replace it by an atomic integer
which is allowed to wrap around.

Signed-off-by: Richard Weinberger <richard@nod.at>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: e9be9d5e76e3 ("overlay filesystem")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/overlayfs/dir.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -12,6 +12,7 @@
 #include <linux/xattr.h>
 #include <linux/security.h>
 #include <linux/cred.h>
+#include <linux/atomic.h>
 #include "overlayfs.h"
 
 void ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
@@ -35,8 +36,10 @@ struct dentry *ovl_lookup_temp(struct de
 {
 	struct dentry *temp;
 	char name[20];
+	static atomic_t temp_id = ATOMIC_INIT(0);
 
-	snprintf(name, sizeof(name), "#%lx", (unsigned long) dentry);
+	/* counter is allowed to wrap, since temp dentries are ephemeral */
+	snprintf(name, sizeof(name), "#%x", atomic_inc_return(&temp_id));
 
 	temp = lookup_one_len(name, workdir, strlen(name));
 	if (!IS_ERR(temp) && temp->d_inode) {

Thread

[PATCH 4.4 000/112] 4.4.28-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 14:50 +0200
  [PATCH 4.4 061/112] NFSv4: Dont report revoked delegations as valid in nfs_have_delegation() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 084/112] irqchip/gicv3: Handle loop timeout proper Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 028/112] powerpc/powernv: Use CPU-endian hub diag-data type in pnv_eeh_get_and_dump_hub_diag() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 051/112] ALSA: hda - Fix a failure of micmute led when having multi adcs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 074/112] Clarify locking of cifs file and tcon structures and make more granular Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 027/112] powerpc/powernv: Pass CPU-endian PE number to opal_pci_eeh_freeze_clear() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 071/112] fs/super.c: fix race between freeze_super() and thaw_super() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 077/112] SMB3: GUIDs should be constructed as random but valid uuids Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 019/112] perf intel-pt: Fix snapshot overlap detection decoder errors Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 024/112] dm mpath: check if paths request_queue is dying in activate_path() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 072/112] cifs: Limit the overall credit acquired Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 070/112] arc: dont leak bits of kernel stack into coredump Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 057/112] Input: i8042 - skip selftest on ASUS laptops Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 054/112] lib: move strtobool() to kstrtobool() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 037/112] zfcp: restore: Dont use 0 to indicate invalid LUN in rec trace Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 058/112] Input: elantech - force needed quirks on Fujitsu H760 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 055/112] lib: update single-char callers of strtobool() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 060/112] sunrpc: fix write space race causing stalls Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 053/112] MIPS: ptrace: Fix regs_return_value for kernel context Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 056/112] lib: add "on"/"off" support to kstrtobool Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 010/112] platform: dont return 0 from platform_get_irq[_byname]() on error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 047/112] [media] mb86a20s: fix the locking logic Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 022/112] dm: mark request_queue dead before destroying the DM device Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 021/112] perf intel-pt: Fix MTC timestamp calculation for large MTC periods Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 043/112] scsi: zfcp: spin_lock_irqsave() is not nestable Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 017/112] pstore/ram: Use memcpy_toio instead of memcpy Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 041/112] zfcp: fix payload trace length for SAN request&response Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 050/112] [media] cx231xx: fix GPIOs for Pixelview SBTVD hybrid Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 049/112] [media] cx231xx: dont return error on success Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 044/112] fbdev/efifb: Fix 16 color palette entry calculation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 048/112] [media] mb86a20s: fix demod settings Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 015/112] pstore/ramoops: fixup driver removal Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 032/112] ubi: Deal with interrupted erasures in WL Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 046/112] ovl: copy_up_xattr(): use strnlen Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 036/112] zfcp: retain trace level for SCSI and HBA FSF response records Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 013/112] parisc: Fix kernel memory layout regarding position of __gp Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 011/112] cpufreq: intel_pstate: Fix unsafe HWP MSR access Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 038/112] zfcp: trace on request for open and close of WKA port Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 035/112] zfcp: close window with unblocked rport during rport gone Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 034/112] zfcp: fix ELS/GS request&response length for hardware data router Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 042/112] zfcp: trace full payload of all SAN records (req,resp,iels) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 040/112] zfcp: fix D_ID field with actual value on tracing SAN responses Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 045/112] ovl: Fix info leak in ovl_lookup_temp() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 033/112] zfcp: fix fc_host port_type with NPIV Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  Re: [PATCH 4.4 000/112] 4.4.28-stable review Shuah Khan <shuah.kh@samsung.com> - 2016-10-26 20:50 +0200
  Re: [PATCH 4.4 000/112] 4.4.28-stable review Guenter Roeck <linux@roeck-us.net> - 2016-10-26 23:50 +0200

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