linux/kernel/bpf
Paul Chaignon c6a9efa1d8 bpf: mark registers in all frames after pkt/null checks
In case of a null check on a pointer inside a subprog, we should mark all
registers with this pointer as either safe or unknown, in both the current
and previous frames.  Currently, only spilled registers and registers in
the current frame are marked.  Packet bound checks in subprogs have the
same issue.  This patch fixes it to mark registers in previous frames as
well.

A good reproducer for null checks looks as follow:

1: ptr = bpf_map_lookup_elem(map, &key);
2: ret = subprog(ptr) {
3:   return ptr != NULL;
4: }
5: if (ret)
6:   value = *ptr;

With the above, the verifier will complain on line 6 because it sees ptr
as map_value_or_null despite the null check in subprog 1.

Note that this patch fixes another resulting bug when using
bpf_sk_release():

1: sk = bpf_sk_lookup_tcp(...);
2: subprog(sk) {
3:   if (sk)
4:     bpf_sk_release(sk);
5: }
6: if (!sk)
7:   return 0;
8: return 1;

In the above, mark_ptr_or_null_regs will warn on line 6 because it will
try to free the reference state, even though it was already freed on
line 3.

Fixes: f4d7e40a5b ("bpf: introduce function calls (verification)")
Signed-off-by: Paul Chaignon <paul.chaignon@orange.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-04-25 17:20:06 -07:00
..
arraymap.c bpf: introduce BPF_F_LOCK flag 2019-02-01 20:55:39 +01:00
bpf_lru_list.c bpf: lru: Lower the PERCPU_NR_SCANS from 16 to 4 2017-04-17 13:55:52 -04:00
bpf_lru_list.h bpf: Only set node->ref = 1 if it has not been set 2017-09-01 09:57:39 -07:00
btf.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-08 15:00:17 -08:00
cgroup.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-08 15:00:17 -08:00
core.c Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-03-06 07:59:36 -08:00
cpumap.c xdp: fix cpumap redirect SKB creation bug 2019-03-29 12:15:02 -07:00
devmap.c bpf: devmap: fix wrong interface selection in notifier_call 2018-10-26 00:32:21 +02:00
disasm.c bpf: disassembler support JMP32 2019-01-26 13:33:01 -08:00
disasm.h bpf: Remove struct bpf_verifier_env argument from print_bpf_insn 2018-03-23 17:38:57 +01:00
hashtab.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-08 15:00:17 -08:00
helpers.c bpf: introduce BPF_F_LOCK flag 2019-02-01 20:55:39 +01:00
inode.c bpf: fix use after free in bpf_evict_inode 2019-03-26 01:38:49 +01:00
local_storage.c bpf: introduce BPF_F_LOCK flag 2019-02-01 20:55:39 +01:00
lpm_trie.c bpf, lpm: fix lookup bug in map_delete_elem 2019-02-22 16:17:53 +01:00
Makefile bpf: add queue and stack maps 2018-10-19 13:24:31 -07:00
map_in_map.c bpf: set inner_map_meta->spin_lock_off correctly 2019-02-27 17:03:13 -08:00
map_in_map.h bpf: Add syscall lookup support for fd array and htab 2017-06-29 13:13:25 -04:00
offload.c bpf: offload: add priv field for drivers 2019-02-12 17:07:09 +01:00
percpu_freelist.c bpf: fix lockdep false positive in percpu_freelist 2019-01-31 23:18:21 +01:00
percpu_freelist.h bpf: fix lockdep false positive in percpu_freelist 2019-01-31 23:18:21 +01:00
queue_stack_maps.c bpf: fix integer overflow in queue_stack_map 2018-11-22 21:29:40 +01:00
reuseport_array.c bpf: Introduce BPF_MAP_TYPE_REUSEPORT_SOCKARRAY 2018-08-11 01:58:46 +02:00
stackmap.c bpf: fix lockdep false positive in stackmap 2019-02-11 16:36:24 +01:00
syscall.c bpf: Try harder when allocating memory for large maps 2019-03-18 16:48:25 +01:00
tnum.c bpf/verifier: improve register value range tracking with ARSH 2018-04-29 08:45:53 -07:00
verifier.c bpf: mark registers in all frames after pkt/null checks 2019-04-25 17:20:06 -07:00
xskmap.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-10-19 11:03:06 -07:00