bpf: Fix invalid mem access when update_effective_progs fails in __cgroup_bpf_detach #6363
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…roup_bpf_detach
Syzkaller triggers an invalid memory access issue following fault
injection in update_effective_progs. The issue can be described as
follows:
__cgroup_bpf_detach
update_effective_progs
compute_effective_progs
bpf_prog_array_alloc <-- fault inject
purge_effective_progs
/* change to dummy_bpf_prog */
array->items[index] = &dummy_bpf_prog.prog
---softirq start---
__do_softirq
...
__cgroup_bpf_run_filter_skb
__bpf_prog_run_save_cb
bpf_prog_run
stats = this_cpu_ptr(prog->stats)
/* invalid memory access */
flags = u64_stats_update_begin_irqsave(&stats->syncp)
---softirq end---
static_branch_dec(&cgroup_bpf_enabled_key[atype])
The reason is that fault injection caused update_effective_progs to fail
and then changed the original prog into dummy_bpf_prog.prog in
purge_effective_progs. Then a softirq came, and accessing the members of
dummy_bpf_prog.prog in the softirq triggers invalid mem access.
To fix it, we can skip updating stats when stats is NULL.
Fixes: 4c46091 ("bpf: Fix KASAN use-after-free Read in compute_effective_progs")
Signed-off-by: Pu Lehui <[email protected]>
Author
|
Upstream branch: 7a0892d |
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Pull request for series with
subject: bpf: Fix invalid mem access when update_effective_progs fails in __cgroup_bpf_detach
version: 4
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1023798