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Issue 1150
Starred by 2 users
Status: Fixed
Owner:
mjurczyk@google.com
Closed: Jun 13
Cc:
project-...@google.com



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 Windows Kernel Mountmgr pool memory disclosure in the handling of IOCTL_MOUNTMGR_QUERY_POINTS
Project Member Reported by mjurczyk@google.com, Feb 24 2017 Back to list 
We have discovered that the handler of the IOCTL_MOUNTMGR_QUERY_POINTS IOCTL in mountmgr.sys discloses portions of uninitialized pool memory to user-mode clients, due to output structure alignment holes.

On our test Windows 7 32-bit workstation, an example layout of the output buffer is as follows:

--- cut ---
00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ff ff ................
00000020: 00 00 00 00 00 00 ff ff 00 00 00 00 00 00 ff ff ................
00000030: 00 00 00 00 00 00 ff ff 00 00 00 00 00 00 ff ff ................
00000040: 00 00 00 00 00 00 ff ff 00 00 00 00 00 00 ff ff ................
00000050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000090: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000000a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000000b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000000c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000000d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000000e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000000f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000110: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000120: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000130: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000140: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000150: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000160: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000170: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000190: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
--- cut ---

Where 00 denote bytes which are properly initialized, while ff indicate uninitialized values copied back to user-mode. The output data is returned in a MOUNTMGR_MOUNT_POINTS structure [1], which in turn contains a list of MOUNTMGR_MOUNT_POINT structures [2]. If we map the above shadow bytes to the structure definitions, it turns out that the repeating pairs of uninitialized bytes correspond to alignment holes after the SymbolicLinkNameLength, UniqueIdLength and DeviceNameLength fields (all of type USHORT, followed by LONG fields, which must be 4-aligned). The concrete number of leaked bytes depends on the number of entries returned by the IOCTL.

The issue can be reproduced by running the attached proof-of-concept program on a system with the Special Pools mechanism enabled for ntoskrnl.exe. Then, it is clearly visible that bytes at the aforementioned offsets are equal to the markers inserted by Special Pools, and would otherwise contain leftover data that was previously stored in that memory region:

--- cut ---
00000000: 56 03 00 00 05 00 00 00 ba 00 00 00 60 00 00 00 V...........`...
00000010: 80 00 00 00 0c 00 00 00 8c 00 00 00 2e 00[67 67]..............gg
00000020: 54 01 00 00 1c 00[67 67]1a 01 00 00 0c 00[67 67]T.....gg......gg
00000030: 26 01 00 00 2e 00[67 67]70 01 00 00 60 00[67 67]&.....ggp...`.gg
00000040: 1a 01 00 00 0c 00[67 67]26 01 00 00 2e 00[67 67]......gg&.....gg
00000050: da 02 00 00 60 00[67 67]d0 01 00 00 ee 00[67 67]....`.gg......gg
00000060: be 02 00 00 1c 00[67 67]3a 03 00 00 1c 00[67 67]......gg:.....gg
00000070: d0 01 00 00 ee 00[67 67]be 02 00 00 1c 00[67 67]......gg......gg
00000080: ee a2 5d 9f 00 00 10 00 00 00 00 00 5c 00 44 00 ..].........\.D.
00000090: 65 00 76 00 69 00 63 00 65 00 5c 00 48 00 61 00 e.v.i.c.e.\.H.a.
000000a0: 72 00 64 00 64 00 69 00 73 00 6b 00 56 00 6f 00 r.d.d.i.s.k.V.o.
000000b0: 6c 00 75 00 6d 00 65 00 31 00 5c 00 3f 00 3f 00 l.u.m.e.1.\.?.?.
000000c0: 5c 00 56 00 6f 00 6c 00 75 00 6d 00 65 00 7b 00 \.V.o.l.u.m.e.{.
000000d0: 62 00 63 00 30 00 35 00 62 00 34 00 39 00 34 00 b.c.0.5.b.4.9.4.
000000e0: 2d 00 64 00 38 00 34 00 37 00 2d 00 31 00 31 00 -.d.8.4.7.-.1.1.
000000f0: 65 00 34 00 2d 00 61 00 33 00 30 00 64 00 2d 00 e.4.-.a.3.0.d.-.
00000100: 38 00 30 00 36 00 65 00 36 00 66 00 36 00 65 00 8.0.6.e.6.f.6.e.
00000110: 36 00 39 00 36 00 33 00 7d 00 ee a2 5d 9f 00 00 6.9.6.3.}...]...
00000120: 50 06 00 00 00 00 5c 00 44 00 65 00 76 00 69 00 P.....\.D.e.v.i.
00000130: 63 00 65 00 5c 00 48 00 61 00 72 00 64 00 64 00 c.e.\.H.a.r.d.d.
00000140: 69 00 73 00 6b 00 56 00 6f 00 6c 00 75 00 6d 00 i.s.k.V.o.l.u.m.
00000150: 65 00 32 00 5c 00 44 00 6f 00 73 00 44 00 65 00 e.2.\.D.o.s.D.e.
00000160: 76 00 69 00 63 00 65 00 73 00 5c 00 43 00 3a 00 v.i.c.e.s.\.C.:.
00000170: 5c 00 3f 00 3f 00 5c 00 56 00 6f 00 6c 00 75 00 \.?.?.\.V.o.l.u.
00000180: 6d 00 65 00 7b 00 62 00 63 00 30 00 35 00 62 00 m.e.{.b.c.0.5.b.
00000190: 34 00 39 00 35 00 2d 00 64 00 38 00 34 00 37 00 4.9.5.-.d.8.4.7.
000001a0: 2d 00 31 00 31 00 65 00 34 00 2d 00 61 00 33 00 -.1.1.e.4.-.a.3.
000001b0: 30 00 64 00 2d 00 38 00 30 00 36 00 65 00 36 00 0.d.-.8.0.6.e.6.
000001c0: 66 00 36 00 65 00 36 00 39 00 36 00 33 00 7d 00 f.6.e.6.9.6.3.}.
000001d0: 5c 00 3f 00 3f 00 5c 00 49 00 44 00 45 00 23 00 \.?.?.\.I.D.E.#.
000001e0: 43 00 64 00 52 00 6f 00 6d 00 56 00 42 00 4f 00 C.d.R.o.m.V.B.O.
000001f0: 58 00 5f 00 43 00 44 00 2d 00 52 00 4f 00 4d 00 X._.C.D.-.R.O.M.
00000200: 5f 00 5f 00 5f 00 5f 00 5f 00 5f 00 5f 00 5f 00 _._._._._._._._.
00000210: 5f 00 5f 00 5f 00 5f 00 5f 00 5f 00 5f 00 5f 00 _._._._._._._._.
00000220: 5f 00 5f 00 5f 00 5f 00 5f 00 5f 00 5f 00 5f 00 _._._._._._._._.
00000230: 5f 00 5f 00 5f 00 5f 00 5f 00 31 00 2e 00 30 00 _._._._._.1...0.
00000240: 5f 00 5f 00 5f 00 5f 00 5f 00 23 00 35 00 26 00 _._._._._.#.5.&.
00000250: 31 00 30 00 36 00 61 00 66 00 31 00 37 00 31 00 1.0.6.a.f.1.7.1.
00000260: 26 00 30 00 26 00 31 00 2e 00 30 00 2e 00 30 00 &.0.&.1...0...0.
00000270: 23 00 7b 00 35 00 33 00 66 00 35 00 36 00 33 00 #.{.5.3.f.5.6.3.
00000280: 30 00 64 00 2d 00 62 00 36 00 62 00 66 00 2d 00 0.d.-.b.6.b.f.-.
00000290: 31 00 31 00 64 00 30 00 2d 00 39 00 34 00 66 00 1.1.d.0.-.9.4.f.
000002a0: 32 00 2d 00 30 00 30 00 61 00 30 00 63 00 39 00 2.-.0.0.a.0.c.9.
000002b0: 31 00 65 00 66 00 62 00 38 00 62 00 7d 00 5c 00 1.e.f.b.8.b.}.\.
000002c0: 44 00 65 00 76 00 69 00 63 00 65 00 5c 00 43 00 D.e.v.i.c.e.\.C.
000002d0: 64 00 52 00 6f 00 6d 00 30 00 5c 00 3f 00 3f 00 d.R.o.m.0.\.?.?.
000002e0: 5c 00 56 00 6f 00 6c 00 75 00 6d 00 65 00 7b 00 \.V.o.l.u.m.e.{.
000002f0: 62 00 63 00 30 00 35 00 62 00 34 00 39 00 38 00 b.c.0.5.b.4.9.8.
00000300: 2d 00 64 00 38 00 34 00 37 00 2d 00 31 00 31 00 -.d.8.4.7.-.1.1.
00000310: 65 00 34 00 2d 00 61 00 33 00 30 00 64 00 2d 00 e.4.-.a.3.0.d.-.
00000320: 38 00 30 00 36 00 65 00 36 00 66 00 36 00 65 00 8.0.6.e.6.f.6.e.
00000330: 36 00 39 00 36 00 33 00 7d 00 5c 00 44 00 6f 00 6.9.6.3.}.\.D.o.
00000340: 73 00 44 00 65 00 76 00 69 00 63 00 65 00 73 00 s.D.e.v.i.c.e.s.
00000350: 5c 00 44 00 3a 00 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? \.D.:...........
--- cut ---

Repeatedly triggering the vulnerability could allow local authenticated attackers to defeat certain exploit mitigations (kernel ASLR) or read other secrets stored in the kernel address space.

This bug is subject to a 90 day disclosure deadline. After 90 days elapse or a patch has been made broadly available, the bug report will become visible to the public.

References:
[1] MOUNTMGR_MOUNT_POINTS structure, https://msdn.microsoft.com/en-us/library/ff562288(v=vs.85).aspx
[2] MOUNTMGR_MOUNT_POINT structure, https://msdn.microsoft.com/en-us/library/ff562286(v=vs.85).aspx
MountmgrQueryPoints.cpp
2.1 KB View Download
Project Member Comment 1 by mjurczyk@google.com, Feb 27 2017
Description: Show this description
Project Member Comment 2 by mjurczyk@google.com, Mar 1 2017
Labels: Reported-2017-Mar-1
Project Member Comment 3 by mjurczyk@google.com, Mar 1 2017
Labels: MSRC-37640
Project Member Comment 4 by mjurczyk@google.com, Mar 9 2017
Labels: Deadline-Exceeded Deadline-Grace
MSRC have requested the grace period extension aiming to fix on June 2017 Patch Tuesday.
Project Member Comment 5 by mjurczyk@google.com, May 20 2017
Labels: CVE-2017-8488
Project Member Comment 6 by mjurczyk@google.com, Jun 13
Labels: Fixed-2017-Jun-13
Status: Fixed
Fixed in today's Patch Tuesday.
Project Member Comment 7 by mjurczyk@google.com, Jun 20
Labels: -restrict-view-commit
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