From: Greg Kroah-Hartman Date: Thu, 9 Jan 2020 19:53:56 +0000 (+0100) Subject: 4.9-stable patches X-Git-Tag: v4.4.209~31 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=76f10c109aed339079a1e85894848ee7dda0ae38;p=thirdparty%2Fkernel%2Fstable-queue.git 4.9-stable patches added patches: bpf-fix-passing-modified-ctx-to-ld-abs-ind-instruction.patch --- diff --git a/queue-4.9/bpf-fix-passing-modified-ctx-to-ld-abs-ind-instruction.patch b/queue-4.9/bpf-fix-passing-modified-ctx-to-ld-abs-ind-instruction.patch new file mode 100644 index 00000000000..de409d120bd --- /dev/null +++ b/queue-4.9/bpf-fix-passing-modified-ctx-to-ld-abs-ind-instruction.patch @@ -0,0 +1,117 @@ +From 6d4f151acf9a4f6fab09b615f246c717ddedcf0c Mon Sep 17 00:00:00 2001 +From: Daniel Borkmann +Date: Mon, 6 Jan 2020 22:51:57 +0100 +Subject: bpf: Fix passing modified ctx to ld/abs/ind instruction + +From: Daniel Borkmann + +commit 6d4f151acf9a4f6fab09b615f246c717ddedcf0c upstream. + +Anatoly has been fuzzing with kBdysch harness and reported a KASAN +slab oob in one of the outcomes: + + [...] + [ 77.359642] BUG: KASAN: slab-out-of-bounds in bpf_skb_load_helper_8_no_cache+0x71/0x130 + [ 77.360463] Read of size 4 at addr ffff8880679bac68 by task bpf/406 + [ 77.361119] + [ 77.361289] CPU: 2 PID: 406 Comm: bpf Not tainted 5.5.0-rc2-xfstests-00157-g2187f215eba #1 + [ 77.362134] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 + [ 77.362984] Call Trace: + [ 77.363249] dump_stack+0x97/0xe0 + [ 77.363603] print_address_description.constprop.0+0x1d/0x220 + [ 77.364251] ? bpf_skb_load_helper_8_no_cache+0x71/0x130 + [ 77.365030] ? bpf_skb_load_helper_8_no_cache+0x71/0x130 + [ 77.365860] __kasan_report.cold+0x37/0x7b + [ 77.366365] ? bpf_skb_load_helper_8_no_cache+0x71/0x130 + [ 77.366940] kasan_report+0xe/0x20 + [ 77.367295] bpf_skb_load_helper_8_no_cache+0x71/0x130 + [ 77.367821] ? bpf_skb_load_helper_8+0xf0/0xf0 + [ 77.368278] ? mark_lock+0xa3/0x9b0 + [ 77.368641] ? kvm_sched_clock_read+0x14/0x30 + [ 77.369096] ? sched_clock+0x5/0x10 + [ 77.369460] ? sched_clock_cpu+0x18/0x110 + [ 77.369876] ? bpf_skb_load_helper_8+0xf0/0xf0 + [ 77.370330] ___bpf_prog_run+0x16c0/0x28f0 + [ 77.370755] __bpf_prog_run32+0x83/0xc0 + [ 77.371153] ? __bpf_prog_run64+0xc0/0xc0 + [ 77.371568] ? match_held_lock+0x1b/0x230 + [ 77.371984] ? rcu_read_lock_held+0xa1/0xb0 + [ 77.372416] ? rcu_is_watching+0x34/0x50 + [ 77.372826] sk_filter_trim_cap+0x17c/0x4d0 + [ 77.373259] ? sock_kzfree_s+0x40/0x40 + [ 77.373648] ? __get_filter+0x150/0x150 + [ 77.374059] ? skb_copy_datagram_from_iter+0x80/0x280 + [ 77.374581] ? do_raw_spin_unlock+0xa5/0x140 + [ 77.375025] unix_dgram_sendmsg+0x33a/0xa70 + [ 77.375459] ? do_raw_spin_lock+0x1d0/0x1d0 + [ 77.375893] ? unix_peer_get+0xa0/0xa0 + [ 77.376287] ? __fget_light+0xa4/0xf0 + [ 77.376670] __sys_sendto+0x265/0x280 + [ 77.377056] ? __ia32_sys_getpeername+0x50/0x50 + [ 77.377523] ? lock_downgrade+0x350/0x350 + [ 77.377940] ? __sys_setsockopt+0x2a6/0x2c0 + [ 77.378374] ? sock_read_iter+0x240/0x240 + [ 77.378789] ? __sys_socketpair+0x22a/0x300 + [ 77.379221] ? __ia32_sys_socket+0x50/0x50 + [ 77.379649] ? mark_held_locks+0x1d/0x90 + [ 77.380059] ? trace_hardirqs_on_thunk+0x1a/0x1c + [ 77.380536] __x64_sys_sendto+0x74/0x90 + [ 77.380938] do_syscall_64+0x68/0x2a0 + [ 77.381324] entry_SYSCALL_64_after_hwframe+0x49/0xbe + [ 77.381878] RIP: 0033:0x44c070 + [...] + +After further debugging, turns out while in case of other helper functions +we disallow passing modified ctx, the special case of ld/abs/ind instruction +which has similar semantics (except r6 being the ctx argument) is missing +such check. Modified ctx is impossible here as bpf_skb_load_helper_8_no_cache() +and others are expecting skb fields in original position, hence, add +check_ctx_reg() to reject any modified ctx. Issue was first introduced back +in f1174f77b50c ("bpf/verifier: rework value tracking"). + +Fixes: f1174f77b50c ("bpf/verifier: rework value tracking") +Reported-by: Anatoly Trosinenko +Signed-off-by: Daniel Borkmann +Signed-off-by: Alexei Starovoitov +Link: https://lore.kernel.org/bpf/20200106215157.3553-1-daniel@iogearbox.net +Signed-off-by: Greg Kroah-Hartman + +--- + kernel/bpf/verifier.c | 9 +++++++-- + 1 file changed, 7 insertions(+), 2 deletions(-) + +--- a/kernel/bpf/verifier.c ++++ b/kernel/bpf/verifier.c +@@ -2422,6 +2422,7 @@ static bool may_access_skb(enum bpf_prog + static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn) + { + struct bpf_reg_state *regs = env->cur_state.regs; ++ static const int ctx_reg = BPF_REG_6; + u8 mode = BPF_MODE(insn->code); + struct bpf_reg_state *reg; + int i, err; +@@ -2439,11 +2440,11 @@ static int check_ld_abs(struct bpf_verif + } + + /* check whether implicit source operand (register R6) is readable */ +- err = check_reg_arg(regs, BPF_REG_6, SRC_OP); ++ err = check_reg_arg(regs, ctx_reg, SRC_OP); + if (err) + return err; + +- if (regs[BPF_REG_6].type != PTR_TO_CTX) { ++ if (regs[ctx_reg].type != PTR_TO_CTX) { + verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n"); + return -EINVAL; + } +@@ -2455,6 +2456,10 @@ static int check_ld_abs(struct bpf_verif + return err; + } + ++ err = check_ctx_reg(env, ®s[ctx_reg], ctx_reg); ++ if (err < 0) ++ return err; ++ + /* reset caller saved regs to unreadable */ + for (i = 0; i < CALLER_SAVED_REGS; i++) { + reg = regs + caller_saved[i]; diff --git a/queue-4.9/series b/queue-4.9/series index d8bc8e6320a..ecdca3f3ea2 100644 --- a/queue-4.9/series +++ b/queue-4.9/series @@ -54,3 +54,4 @@ s390-smp-fix-physical-to-logical-cpu-map-for-smt.patch xen-blkback-avoid-unmapping-unmapped-grant-pages.patch locking-x86-remove-the-unused-atomic_inc_short-methd.patch pstore-ram-write-new-dumps-to-start-of-recycled-zone.patch +bpf-fix-passing-modified-ctx-to-ld-abs-ind-instruction.patch