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[PATCH 3.19.y-ckt 10/40] get_rock_ridge_filename(): handle malformed NM entries

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3.19.8-ckt22 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Al Viro <viro@zeniv.linux.org.uk>

commit 99d825822eade8d827a1817357cbf3f889a552d6 upstream.

Payloads of NM entries are not supposed to contain NUL.  When we run
into such, only the part prior to the first NUL goes into the
concatenation (i.e. the directory entry name being encoded by a bunch
of NM entries).  We do stop when the amount collected so far + the
claimed amount in the current NM entry exceed 254.  So far, so good,
but what we return as the total length is the sum of *claimed*
sizes, not the actual amount collected.  And that can grow pretty
large - not unlimited, since you'd need to put CE entries in
between to be able to get more than the maximum that could be
contained in one isofs directory entry / continuation chunk and
we are stop once we'd encountered 32 CEs, but you can get about 8Kb
easily.  And that's what will be passed to readdir callback as the
name length.  8Kb __copy_to_user() from a buffer allocated by
__get_free_page()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 fs/isofs/rock.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/fs/isofs/rock.c b/fs/isofs/rock.c
index 735d752..204659a 100644
--- a/fs/isofs/rock.c
+++ b/fs/isofs/rock.c
@@ -203,6 +203,8 @@ int get_rock_ridge_filename(struct iso_directory_record *de,
 	int retnamlen = 0;
 	int truncate = 0;
 	int ret = 0;
+	char *p;
+	int len;
 
 	if (!ISOFS_SB(inode->i_sb)->s_rock)
 		return 0;
@@ -267,12 +269,17 @@ repeat:
 					rr->u.NM.flags);
 				break;
 			}
-			if ((strlen(retname) + rr->len - 5) >= 254) {
+			len = rr->len - 5;
+			if (retnamlen + len >= 254) {
 				truncate = 1;
 				break;
 			}
-			strncat(retname, rr->u.NM.name, rr->len - 5);
-			retnamlen += rr->len - 5;
+			p = memchr(rr->u.NM.name, '\0', len);
+			if (unlikely(p))
+				len = p - rr->u.NM.name;
+			memcpy(retname + retnamlen, rr->u.NM.name, len);
+			retnamlen += len;
+			retname[retnamlen] = '\0';
 			break;
 		case SIG('R', 'E'):
 			kfree(rs.buffer);
-- 
2.7.4

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[3.19.y-ckt stable] Linux 3.19.8-ckt22 stable review Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 29/40] ipv4/fib: don't warn when primary address is missing if in_dev is dead Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 39/40] net: bridge: fix old ioctl unlocked net device walk Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 26/40] route: do not cache fib route info on local routes with oif Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 20/40] net: fec: only clear a queue's work bit if the queue was emptied Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 10/40] get_rock_ridge_filename(): handle malformed NM entries Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 30/40] bpf: fix double-fdput in replace_map_fd_with_map_ptr() Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 19/40] nf_conntrack: avoid kernel pointer value leak in slab name Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 15/40] tools lib traceevent: Free filter tokens in process_filter() Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 02/40] [3.19-stable only] fix backport "IB/security: restrict use of the write() interface" Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 21/40] net/mlx4_en: Fix endianness bug in IPV6 csum calculation Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
    RE: [PATCH 3.19.y-ckt 21/40] net/mlx4_en: Fix endianness bug in IPV6  csum calculation Tariq Toukan <tariqt@mellanox.com> - 2016-05-26 11:00 +0200
  [PATCH 3.19.y-ckt 23/40] tcp: refresh skb timestamp at retransmit time Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 25/40] decnet: Do not build routes to devices without decnet private data. Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 31/40] net_sched: introduce qdisc_replace() helper Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 34/40] sch_dsmark: update backlog as well Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 40/40] net: fix a kernel infoleak in x25 module Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 24/40] arm64: bpf: jit JMP_JSET_{X,K} Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 28/40] vlan: pull on __vlan_insert_tag error path and fix csum correction Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 18/40] ocfs2: fix posix_acl_create deadlock Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:40 +0200
  [PATCH 3.19.y-ckt 16/40] tools lib traceevent: Do not reassign parg after collapse_tree() Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:50 +0200
  [PATCH 3.19.y-ckt 03/40] Revert "usb: hub: do not clear BOS field during reset device" Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:50 +0200
  [PATCH 3.19.y-ckt 09/40] drm/radeon: fix PLL sharing on DCE6.1 (v2) Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:50 +0200
  [PATCH 3.19.y-ckt 13/40] drm/i915: Bail out of pipe config compute loop on LPT Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:50 +0200
  [PATCH 3.19.y-ckt 01/40] compiler-gcc: integrate the various compiler-gcc[345].h files Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:50 +0200
  [PATCH 3.19.y-ckt 06/40] regmap: spmi: Fix regmap_spmi_ext_read in multi-byte case Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:50 +0200
  [PATCH 3.19.y-ckt 14/40] ALSA: hda - Fix subwoofer pin on ASUS N751 and N551 Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:50 +0200
  [PATCH 3.19.y-ckt 12/40] Input: max8997-haptic - fix NULL pointer dereference Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:50 +0200
  [PATCH 3.19.y-ckt 05/40] regulator: s2mps11: Fix invalid selector mask and voltages for buck9 Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:50 +0200
  [PATCH 3.19.y-ckt 08/40] crypto: hash - Fix page length clamping in hash walk Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:50 +0200
  [PATCH 3.19.y-ckt 04/40] [3.19-stable] x86: LLVMLinux: Fix "incomplete type const struct x86cpu_device_id" Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:50 +0200
  [PATCH 3.19.y-ckt 11/40] ALSA: hda - Fix white noise on Asus UX501VW headset Kamal Mostafa <kamal@canonical.com> - 2016-05-25 19:50 +0200

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