From: Sasha Levin Date: Sun, 6 Oct 2019 00:48:58 +0000 (-0400) Subject: fixes for 4.14 X-Git-Tag: v4.9.196~25^2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8eaa0f2ace4a0b71ab80f0074ea4f63213332930;p=thirdparty%2Fkernel%2Fstable-queue.git fixes for 4.14 Signed-off-by: Sasha Levin --- diff --git a/queue-4.14/bpf-fix-use-after-free-in-prog-symbol-exposure.patch b/queue-4.14/bpf-fix-use-after-free-in-prog-symbol-exposure.patch new file mode 100644 index 00000000000..4e08e477313 --- /dev/null +++ b/queue-4.14/bpf-fix-use-after-free-in-prog-symbol-exposure.patch @@ -0,0 +1,132 @@ +From 70d4e286616c2f5aa370f250e9deaeaf27379144 Mon Sep 17 00:00:00 2001 +From: Sasha Levin +Date: Fri, 4 Oct 2019 10:41:12 -0700 +Subject: bpf: fix use after free in prog symbol exposure + +From: Daniel Borkmann + +commit c751798aa224fadc5124b49eeb38fb468c0fa039 upstream. + +syzkaller managed to trigger the warning in bpf_jit_free() which checks via +bpf_prog_kallsyms_verify_off() for potentially unlinked JITed BPF progs +in kallsyms, and subsequently trips over GPF when walking kallsyms entries: + + [...] + 8021q: adding VLAN 0 to HW filter on device batadv0 + 8021q: adding VLAN 0 to HW filter on device batadv0 + WARNING: CPU: 0 PID: 9869 at kernel/bpf/core.c:810 bpf_jit_free+0x1e8/0x2a0 + Kernel panic - not syncing: panic_on_warn set ... + CPU: 0 PID: 9869 Comm: kworker/0:7 Not tainted 5.0.0-rc8+ #1 + Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 + Workqueue: events bpf_prog_free_deferred + Call Trace: + __dump_stack lib/dump_stack.c:77 [inline] + dump_stack+0x113/0x167 lib/dump_stack.c:113 + panic+0x212/0x40b kernel/panic.c:214 + __warn.cold.8+0x1b/0x38 kernel/panic.c:571 + report_bug+0x1a4/0x200 lib/bug.c:186 + fixup_bug arch/x86/kernel/traps.c:178 [inline] + do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271 + do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290 + invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973 + RIP: 0010:bpf_jit_free+0x1e8/0x2a0 + Code: 02 4c 89 e2 83 e2 07 38 d0 7f 08 84 c0 0f 85 86 00 00 00 48 ba 00 02 00 00 00 00 ad de 0f b6 43 02 49 39 d6 0f 84 5f fe ff ff <0f> 0b e9 58 fe ff ff 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 + RSP: 0018:ffff888092f67cd8 EFLAGS: 00010202 + RAX: 0000000000000007 RBX: ffffc90001947000 RCX: ffffffff816e9d88 + RDX: dead000000000200 RSI: 0000000000000008 RDI: ffff88808769f7f0 + RBP: ffff888092f67d00 R08: fffffbfff1394059 R09: fffffbfff1394058 + R10: fffffbfff1394058 R11: ffffffff89ca02c7 R12: ffffc90001947002 + R13: ffffc90001947020 R14: ffffffff881eca80 R15: ffff88808769f7e8 + BUG: unable to handle kernel paging request at fffffbfff400d000 + #PF error: [normal kernel read fault] + PGD 21ffee067 P4D 21ffee067 PUD 21ffed067 PMD 9f942067 PTE 0 + Oops: 0000 [#1] PREEMPT SMP KASAN + CPU: 0 PID: 9869 Comm: kworker/0:7 Not tainted 5.0.0-rc8+ #1 + Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 + Workqueue: events bpf_prog_free_deferred + RIP: 0010:bpf_get_prog_addr_region kernel/bpf/core.c:495 [inline] + RIP: 0010:bpf_tree_comp kernel/bpf/core.c:558 [inline] + RIP: 0010:__lt_find include/linux/rbtree_latch.h:115 [inline] + RIP: 0010:latch_tree_find include/linux/rbtree_latch.h:208 [inline] + RIP: 0010:bpf_prog_kallsyms_find+0x107/0x2e0 kernel/bpf/core.c:632 + Code: 00 f0 ff ff 44 38 c8 7f 08 84 c0 0f 85 fa 00 00 00 41 f6 45 02 01 75 02 0f 0b 48 39 da 0f 82 92 00 00 00 48 89 d8 48 c1 e8 03 <42> 0f b6 04 30 84 c0 74 08 3c 03 0f 8e 45 01 00 00 8b 03 48 c1 e0 + [...] + +Upon further debugging, it turns out that whenever we trigger this +issue, the kallsyms removal in bpf_prog_ksym_node_del() was /skipped/ +but yet bpf_jit_free() reported that the entry is /in use/. + +Problem is that symbol exposure via bpf_prog_kallsyms_add() but also +perf_event_bpf_event() were done /after/ bpf_prog_new_fd(). Once the +fd is exposed to the public, a parallel close request came in right +before we attempted to do the bpf_prog_kallsyms_add(). + +Given at this time the prog reference count is one, we start to rip +everything underneath us via bpf_prog_release() -> bpf_prog_put(). +The memory is eventually released via deferred free, so we're seeing +that bpf_jit_free() has a kallsym entry because we added it from +bpf_prog_load() but /after/ bpf_prog_put() from the remote CPU. + +Therefore, move both notifications /before/ we install the fd. The +issue was never seen between bpf_prog_alloc_id() and bpf_prog_new_fd() +because upon bpf_prog_get_fd_by_id() we'll take another reference to +the BPF prog, so we're still holding the original reference from the +bpf_prog_load(). + +Fixes: 6ee52e2a3fe4 ("perf, bpf: Introduce PERF_RECORD_BPF_EVENT") +Fixes: 74451e66d516 ("bpf: make jited programs visible in traces") +Reported-by: syzbot+bd3bba6ff3fcea7a6ec6@syzkaller.appspotmail.com +Signed-off-by: Daniel Borkmann +Cc: Song Liu +Signed-off-by: Zubin Mithra +Signed-off-by: Sasha Levin +--- + kernel/bpf/syscall.c | 30 ++++++++++++++++++------------ + 1 file changed, 18 insertions(+), 12 deletions(-) + +diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c +index 2d828d3469822..59d2e94ecb798 100644 +--- a/kernel/bpf/syscall.c ++++ b/kernel/bpf/syscall.c +@@ -1067,20 +1067,26 @@ static int bpf_prog_load(union bpf_attr *attr) + if (err) + goto free_used_maps; + +- err = bpf_prog_new_fd(prog); +- if (err < 0) { +- /* failed to allocate fd. +- * bpf_prog_put() is needed because the above +- * bpf_prog_alloc_id() has published the prog +- * to the userspace and the userspace may +- * have refcnt-ed it through BPF_PROG_GET_FD_BY_ID. +- */ +- bpf_prog_put(prog); +- return err; +- } +- ++ /* Upon success of bpf_prog_alloc_id(), the BPF prog is ++ * effectively publicly exposed. However, retrieving via ++ * bpf_prog_get_fd_by_id() will take another reference, ++ * therefore it cannot be gone underneath us. ++ * ++ * Only for the time /after/ successful bpf_prog_new_fd() ++ * and before returning to userspace, we might just hold ++ * one reference and any parallel close on that fd could ++ * rip everything out. Hence, below notifications must ++ * happen before bpf_prog_new_fd(). ++ * ++ * Also, any failure handling from this point onwards must ++ * be using bpf_prog_put() given the program is exposed. ++ */ + bpf_prog_kallsyms_add(prog); + trace_bpf_prog_load(prog, err); ++ ++ err = bpf_prog_new_fd(prog); ++ if (err < 0) ++ bpf_prog_put(prog); + return err; + + free_used_maps: +-- +2.20.1 + diff --git a/queue-4.14/series b/queue-4.14/series index 6f66c149927..c936ca1c3e1 100644 --- a/queue-4.14/series +++ b/queue-4.14/series @@ -46,3 +46,4 @@ hypfs-fix-error-number-left-in-struct-pointer-member.patch kbuild-clean-compressed-initramfs-image.patch ocfs2-wait-for-recovering-done-after-direct-unlock-r.patch kmemleak-increase-debug_kmemleak_early_log_size-defa.patch +bpf-fix-use-after-free-in-prog-symbol-exposure.patch