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| author | Hui Su <sh_def@163.com> | 2026-08-14 00:09:00 +0800 |
|---|---|---|
| committer | Andrii Nakryiko <andrii@kernel.org> | 2026-08-21 10:41:11 -0700 |
| commit | ed54bf564ac52699cf4def3d0c2125d493e756f9 (patch) | |
| tree | 401501569cbac5f6137c0878909bfb19db39dde3 /include | |
| parent | efebf6496685c93150df5bb0794363ae70c5f58a (diff) | |
| download | linux-ed54bf564ac52699cf4def3d0c2125d493e756f9.tar.gz linux-ed54bf564ac52699cf4def3d0c2125d493e756f9.zip | |
bpf: Fix BPF_F_CPU validation for sparse CPU IDs
BPF_F_CPU stores the target CPU ID in the upper 32 bits of the map
operation flags. bpf_map_check_op_flags() currently compares that ID
with num_possible_cpus(), which is the number of possible CPUs rather
than a bound on CPU IDs.
On an arm64 QEMU guest with a CPU device-tree hole, the possible CPU
mask was 0,2-3. A userspace program using raw bpf() syscalls creates
a BPF_MAP_TYPE_PERCPU_ARRAY and performs update and lookup operations
for each CPU by setting BPF_F_CPU and the CPU ID in the flags.
With the old check, CPU 1 is incorrectly accepted while valid CPU 3 is
rejected with -ERANGE. The CPU 1 update then reaches the per-CPU map
access path and triggers:
Unable to handle kernel paging request at virtual address ...
pc : __pi_memcpy_generic+0x5c/0x22c
lr : bpf_percpu_array_update+0x2dc/0x2e8
Call trace:
__pi_memcpy_generic
bpf_map_update_value
map_update_elem
__sys_bpf
Check the CPU ID against nr_cpu_ids and cpu_possible() instead. This
rejects CPU IDs outside the valid range and CPUs absent from the
possible mask, while allowing valid sparse CPU IDs.
Fixes: 2b421662c788 ("bpf: Introduce BPF_F_CPU and BPF_F_ALL_CPUS flags")
Signed-off-by: Hui Su <sh_def@163.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/bpf/20260813160858.1042834-3-sh_def@163.com
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/bpf.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index ffa5626411ac..b7dbf3d9b5c0 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -4209,7 +4209,7 @@ static inline int bpf_map_check_op_flags(struct bpf_map *map, u64 flags, u64 all return -EINVAL; cpu = flags >> 32; - if ((flags & BPF_F_CPU) && cpu >= num_possible_cpus()) + if ((flags & BPF_F_CPU) && (cpu >= nr_cpu_ids || !cpu_possible(cpu))) return -ERANGE; } |