linux/kernel/bpf
Eduard Zingerman b0c8e6d3d8 bpf: account for current allocated stack depth in widen_imprecise_scalars()
The usage pattern for widen_imprecise_scalars() looks as follows:

    prev_st = find_prev_entry(env, ...);
    queued_st = push_stack(...);
    widen_imprecise_scalars(env, prev_st, queued_st);

Where prev_st is an ancestor of the queued_st in the explored states
tree. This ancestor is not guaranteed to have same allocated stack
depth as queued_st. E.g. in the following case:

    def main():
      for i in 1..2:
        foo(i)        // same callsite, differnt param

    def foo(i):
      if i == 1:
        use 128 bytes of stack
      iterator based loop

Here, for a second 'foo' call prev_st->allocated_stack is 128,
while queued_st->allocated_stack is much smaller.
widen_imprecise_scalars() needs to take this into account and avoid
accessing bpf_verifier_state->frame[*]->stack out of bounds.

Fixes: 2793a8b015 ("bpf: exact states comparison for iterator convergence checks")
Reported-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20251114025730.772723-1-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-11-14 09:26:05 -08:00
..
preload
Kconfig
Makefile
arena.c
arraymap.c
bloom_filter.c
bpf_cgrp_storage.c
bpf_inode_storage.c
bpf_iter.c
bpf_local_storage.c
bpf_lru_list.c
bpf_lru_list.h
bpf_lsm.c
bpf_struct_ops.c
bpf_task_storage.c
btf.c
btf_iter.c
btf_relocate.c
cgroup.c
cgroup_iter.c
core.c
cpumap.c
cpumask.c
crypto.c
devmap.c
disasm.c
disasm.h
dispatcher.c
dmabuf_iter.c
hashtab.c
helpers.c
inode.c
kmem_cache_iter.c
link_iter.c
liveness.c
local_storage.c
log.c
lpm_trie.c
map_in_map.c
map_in_map.h
map_iter.c
memalloc.c
mmap_unlock_work.h
mprog.c
net_namespace.c
offload.c
percpu_freelist.c
percpu_freelist.h
prog_iter.c
queue_stack_maps.c
range_tree.c
range_tree.h
relo_core.c
reuseport_array.c
ringbuf.c
rqspinlock.c
rqspinlock.h
stackmap.c
stream.c
syscall.c
sysfs_btf.c
task_iter.c
tcx.c
tnum.c
token.c
trampoline.c
verifier.c