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[PATCH 3.19.y-ckt 30/40] bpf: fix double-fdput in replace_map_fd_with_map_ptr()

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

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

From: Jann Horn <jannh@google.com>

[ Upstream commit 8358b02bf67d3a5d8a825070e1aa73f25fb2e4c7 ]

When bpf(BPF_PROG_LOAD, ...) was invoked with a BPF program whose bytecode
references a non-map file descriptor as a map file descriptor, the error
handling code called fdput() twice instead of once (in __bpf_map_get() and
in replace_map_fd_with_map_ptr()). If the file descriptor table of the
current task is shared, this causes f_count to be decremented too much,
allowing the struct file to be freed while it is still in use
(use-after-free). This can be exploited to gain root privileges by an
unprivileged user.

This bug was introduced in
commit 0246e64d9a5f ("bpf: handle pseudo BPF_LD_IMM64 insn"), but is only
exploitable since
commit 1be7f75d1668 ("bpf: enable non-root eBPF programs") because
previously, CAP_SYS_ADMIN was required to reach the vulnerable code.

(posted publicly according to request by maintainer)

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 kernel/bpf/verifier.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 0d2cbc9..45fdf5c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1817,7 +1817,6 @@ static int replace_map_fd_with_map_ptr(struct verifier_env *env)
 			if (IS_ERR(map)) {
 				verbose("fd %d is not pointing to valid bpf_map\n",
 					insn->imm);
-				fdput(f);
 				return PTR_ERR(map);
 			}
 
-- 
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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