diff options
| author | Tony Ambardar <tony.ambardar@gmail.com> | 2020-09-19 22:01:33 -0700 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2020-09-21 21:50:24 +0200 |
| commit | e23bb04b0c938588eae41b7f4712b722290ed2b8 (patch) | |
| tree | 024a12665cf2d599a175be5b5a29d61769dc4e84 /kernel | |
| parent | ba2fd563b7408b8dd9bbd72fcae8bcb3c14e8ec8 (diff) | |
bpf: Fix sysfs export of empty BTF section
If BTF data is missing or removed from the ELF section it is still exported
via sysfs as a zero-length file:
root@OpenWrt:/# ls -l /sys/kernel/btf/vmlinux
-r--r--r-- 1 root root 0 Jul 18 02:59 /sys/kernel/btf/vmlinux
Moreover, reads from this file succeed and leak kernel data:
root@OpenWrt:/# hexdump -C /sys/kernel/btf/vmlinux|head -10
000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
000cc0 00 00 00 00 00 00 00 00 00 00 00 00 80 83 b0 80 |................|
000cd0 00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000ce0 00 00 00 00 00 00 00 00 00 00 00 00 57 ac 6e 9d |............W.n.|
000cf0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
002650 00 00 00 00 00 00 00 10 00 00 00 01 00 00 00 01 |................|
002660 80 82 9a c4 80 85 97 80 81 a9 51 68 00 00 00 02 |..........Qh....|
002670 80 25 44 dc 80 85 97 80 81 a9 50 24 81 ab c4 60 |.%D.......P$...`|
This situation was first observed with kernel 5.4.x, cross-compiled for a
MIPS target system. Fix by adding a sanity-check for export of zero-length
data sections.
Fixes: 341dfcf8d78e ("btf: expose BTF info through sysfs")
Signed-off-by: Tony Ambardar <Tony.Ambardar@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/b38db205a66238f70823039a8c531535864eaac5.1600417359.git.Tony.Ambardar@gmail.com
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/sysfs_btf.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c index 3b495773de5a..11b3380887fa 100644 --- a/kernel/bpf/sysfs_btf.c +++ b/kernel/bpf/sysfs_btf.c @@ -30,15 +30,15 @@ static struct kobject *btf_kobj; static int __init btf_vmlinux_init(void) { - if (!__start_BTF) + bin_attr_btf_vmlinux.size = __stop_BTF - __start_BTF; + + if (!__start_BTF || bin_attr_btf_vmlinux.size == 0) return 0; btf_kobj = kobject_create_and_add("btf", kernel_kobj); if (!btf_kobj) return -ENOMEM; - bin_attr_btf_vmlinux.size = __stop_BTF - __start_BTF; - return sysfs_create_bin_file(btf_kobj, &bin_attr_btf_vmlinux); } |