linux.git/kernel/bpf/verifier.c, branch v7.2-rc2

bpf: Fix insn_aux_data leak on verifier err_free_env path

2026-06-26T01:23:56+00:00

When bpf_check() allocates env->insn_aux_data successfully but later
fails to allocate env->succ, it jumps directly to err_free_env.

The existing vfree(env->insn_aux_data) sits before the err_free_env
label, so that direct jump bypasses it and leaks insn_aux_data.

Move vfree(env->insn_aux_data) into err_free_env so all early and late
exit paths release it consistently.

Fixes: 2f69c5685427 ("bpf: make bpf_insn_successors to return a pointer")
Signed-off-by: KaFai Wan 
Reviewed-by: Anton Protopopov 
Link: https://lore.kernel.org/r/20260624123536.114757-1-kafai.wan@linux.dev
Signed-off-by: Alexei Starovoitov

bpf: Reject offset refcount acquire arguments

2026-06-26T00:51:20+00:00

bpf_refcount_acquire() increments the refcount at the caller-supplied
pointer plus the refcount field offset, then returns the caller-supplied
pointer unchanged.

The verifier records the return value as a base pointer to the refcounted
object.

bpf_list_pop_front() and bpf_rbtree_remove() can return embedded
graph-node pointers as PTR_TO_BTF_ID | MEM_ALLOC with a fixed offset equal
to the node field offset. Passing such a pointer directly to
bpf_refcount_acquire() currently passes the refcounted-kptr type check.

That makes the runtime operation start from base + node_off while the
verifier models the returned pointer as the object base.

Require refcount-acquire arguments to have zero fixed offset by carrying
the requirement through check_func_arg_reg_off() to __check_ptr_off_reg().
Programs can still acquire a refcount from a graph-node-derived pointer
after normalizing it with container_of().

Fixes: 7c50b1cb76aca ("bpf: Add bpf_refcount_acquire kfunc")
Signed-off-by: Yiyang Chen 
Acked-by: Eduard Zingerman 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/r/2f894647f56f71838fdddeb97a3e057ed35ea92e.1782192383.git.chenyy23@mails.tsinghua.edu.cn
Signed-off-by: Alexei Starovoitov

bpf: Reset register bounds before narrowing retval range in check_mem_access()

2026-06-23T00:11:46+00:00

When the BPF verifier processes a context load of an LSM hook return
value, it calls __mark_reg_s32_range() to narrow the register to the
hook's valid range. However, __mark_reg_s32_range() intersects the new
range with the register's existing bounds using max_t()/min_t() rather
than replacing them.

If the destination register carries stale bounds from a prior instruction
(e.g. BPF_MOV64_IMM), the intersection can produce a range narrower than
reality. The verifier then believes it knows the register's exact value,
while at runtime the actual hook return value is loaded, creating a
verifier/runtime mismatch that can be used to bypass BPF memory safety
checks.

The else branch already calls mark_reg_unknown() to reset register state
before any narrowing. Apply the same reset in the is_retval path so
stale bounds are cleared before __mark_reg_s32_range() intersects.

Fixes: 5d99e198be27 ("bpf, lsm: Add check for BPF LSM return value")
Cc: stable@vger.kernel.org
Signed-off-by: Tristan Madani 
Acked-by: Eduard Zingerman 
Link: https://lore.kernel.org/r/20260622230123.3695446-2-tristmd@gmail.com
Signed-off-by: Alexei Starovoitov

bpf: Emit verbose message when prog-specific btf_struct_access rejects a write

2026-06-22T00:58:49+00:00

When BPF_WRITE goes through a PTR_TO_BTF_ID register, check_ptr_to_btf_access()
delegates to env->ops->btf_struct_access(). Most implementations
(bpf_scx_btf_struct_access, tc_cls_act_btf_struct_access, etc.) return
-EACCES for disallowed fields without logging anything, so the verifier
rejects the program with an empty message. For example a scx program doing

  1: R1=trusted_ptr_task_struct()
  ...
  4: (7b) *(u64 *)(r1 +0) = r2
  verification time 83 usec
  the program is rejected

leaves the user guessing which field is off-limits.
Emit verbose message.

Signed-off-by: Alexei Starovoitov 
Reviewed-by: Emil Tsalapatis 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/r/20260615232146.5491-1-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov

bpf: Fix stack slot index in nospec checks

2026-06-22T00:51:58+00:00

check_stack_write_fixed_off() computes the byte slot for a fixed-offset
stack write as -off - 1, and records each written byte in slot_type[] with
(slot - i) % BPF_REG_SIZE.

The Spectre v4 sanitization pre-check uses slot_type[i] instead. For a
4-byte write at fp-8 after the lower half of fp-8 has been zeroed, the
pre-check scans bytes 0..3 and sees STACK_ZERO while the actual write updates
bytes 7..4. That can leave the second half-slot write without nospec_result
even though the bytes being overwritten still require sanitization.

Use the same slot index in the sanitization pre-check that the write path uses
when updating slot_type[].

Fixes: 2039f26f3aca ("bpf: Fix leakage due to insufficient speculative store bypass mitigation")
Acked-by: Luis Gerhorst 
Reviewed-by: Jiayuan Chen 
Reviewed-by: Emil Tsalapatis 
Signed-off-by: Nuoqi Gui 
Link: https://lore.kernel.org/r/20260618-f01-11-stack-nospec-slot-index-v3-1-780297041721@mails.tsinghua.edu.cn
Signed-off-by: Alexei Starovoitov

bpf: Raise maximum call chain depth to 16 frames

2026-06-14T20:47:38+00:00

Bump MAX_CALL_FRAMES from 8 to 16 to allow deeper call chains
that Rust-BPF requires and update selftests.

Link: https://lore.kernel.org/r/20260613180755.29671-1-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov

bpf: Reject bpf_obj_drop() from tracing progs

2026-06-10T04:23:11+00:00

bpf_obj_drop() runs bpf_obj_free_fields() synchronously for
program-allocated objects. When such an object contains NMI unsafe
fields, tracing programs that can run from arbitrary instrumented
context can reach that destruction from unsafe contexts, including NMI.

NMI is likely one instance of this problem, and other instances would
include possible unsafe reentrancy. Deferring bpf_obj_drop() is not
appealing either: it would add delayed-free machinery to a release
operation that otherwise has straightforward synchronous ownership
semantics.

Reject bpf_obj_drop() and bpf_percpu_obj_drop() from tracing programs
that may run from unsafe contexts unless every field in the object's BTF
record is explicitly NMI safe. Do not reject sleepable
BPF_PROG_TYPE_TRACING programs, since they are not the arbitrary/NMI
contexts that motivate the restriction.

Note that while bpf_rb_root and bpf_list_head would be NMI safe on their
own to free, the objects recursively held by them may not be; be
conservative and just mark them as not NMI safe for now.

Use a whitelist for the NMI-safe field set instead of listing only known
NMI unsafe fields. Locks, async fields, unreferenced kptrs, and
refcounts are known to be NMI safe because their destruction is either a
no-op, simple state reset, or async cancellation. Referenced kptrs,
percpu referenced kptrs, uptrs, graph roots, graph nodes, and any future
field type are rejected until audited for arbitrary tracing and NMI
contexts. This is less susceptible to future changes in fields that were
previously safe by exclusion, and to new fields being added without
updating this check.

Convert the existing recursive local-object drop success case to a
syscall program in the same commit, since this verifier change makes the
old tracing program form invalid. The test still exercises
bpf_obj_drop() releasing a referenced task kptr from a safe program
type.

Fixes: ac9f06050a35 ("bpf: Introduce bpf_obj_drop")
Signed-off-by: Justin Suess 
Co-developed-by: Kumar Kartikeya Dwivedi 
Signed-off-by: Kumar Kartikeya Dwivedi 
Link: https://lore.kernel.org/r/20260609202548.3571690-2-memxor@gmail.com
Signed-off-by: Alexei Starovoitov

bpf: Allow sleepable programs to use LPM trie maps directly

2026-06-09T19:42:38+00:00

The previous change relaxed the rcu_dereference annotations in
lpm_trie.c so the trie walks no longer trip lockdep when reached from a
sleepable BPF program holding only rcu_read_lock_trace().  By itself
that only helps tries reached as the inner map of a map-of-maps, or
from the classic-RCU syscall path: a sleepable program that references
an LPM trie directly is still rejected at load time by
check_map_prog_compatibility(), whose sleepable whitelist omits
BPF_MAP_TYPE_LPM_TRIE:

  Sleepable programs can only use array, hash, ringbuf and local storage maps

LPM trie nodes are allocated from a bpf_mem_alloc (trie->ma) and freed
with bpf_mem_cache_free_rcu(), which chains a regular RCU grace period
into a Tasks Trace grace period before the node -- and the value
embedded in it that trie_lookup_elem() returns to the program -- is
released.  That is the same reclaim discipline BPF_MAP_TYPE_HASH relies
on for sleepable access, so a value handed to a sleepable reader cannot
be freed while the program is still running under rcu_read_lock_trace().
The writer paths take trie->lock across the walk and never relied on the
RCU read-side lock to keep nodes alive.

Add BPF_MAP_TYPE_LPM_TRIE to the sleepable map whitelist so these
programs can use LPM tries directly.

Signed-off-by: Vlad Poenaru 
Reviewed-by: Emil Tsalapatis 
Link: https://lore.kernel.org/r/20260609135558.193287-3-vlad.wing@gmail.com
Signed-off-by: Alexei Starovoitov

bpf: Enforce write checks for BTF pointer helper access

2026-06-09T15:39:46+00:00

check_mem_reg() verifies both read and write access for global subprogram
memory arguments. When the caller register is PTR_TO_BTF_ID,
check_helper_mem_access() currently forwards the access to
check_ptr_to_btf_access() as BPF_READ regardless of the requested access
type.

This lets a BTF-backed kernel object field pointer pass the caller-side
writable memory check for a global subprogram argument. The callee is then
validated with a generic writable PTR_TO_MEM argument and can store through
it, even though an equivalent direct BTF field store is rejected with "only
read is supported".

Forward the requested access type to check_ptr_to_btf_access().
This enforces existing BTF write restrictions for global subprogram memory
arguments as well.

Fixes: 3e30be4288b3 ("bpf: Allow helpers access trusted PTR_TO_BTF_ID.")
Signed-off-by: Nuoqi Gui 
Link: https://lore.kernel.org/bpf/20260609-f01-04-btf-writable-arg-v1-1-f449cd970669@mails.tsinghua.edu.cn
Signed-off-by: Kumar Kartikeya Dwivedi

bpf: Keep dynamic inner array lookups nullable

2026-06-08T11:32:52+00:00

An ARRAY_OF_MAPS can use an array created with BPF_F_INNER_MAP as its
inner map template. A concrete inner array with a different max_entries
value can then replace the template.

After a successful outer map lookup, the verifier represents the
resulting map pointer using the inner map template. Const-key lookup
nullness elision consequently uses the template max_entries even though
the runtime helper uses the concrete inner map max_entries.

Do not elide lookup result nullness for maps marked with BPF_F_INNER_MAP,
because the template max_entries does not prove that the key is in bounds
for the concrete runtime map.

Fixes: d2102f2f5d75 ("bpf: verifier: Support eliding map lookup nullness")
Signed-off-by: Nuoqi Gui 
Acked-by: Eduard Zingerman 
Acked-by: Jiri Olsa 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/bpf/20260607-f01-v2-v2-1-da48453146e8@mails.tsinghua.edu.cn
Signed-off-by: Kumar Kartikeya Dwivedi