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authorTony Ambardar <tony.ambardar@gmail.com>2020-09-20 07:01:33 +0200
committerDaniel Borkmann <daniel@iogearbox.net>2020-09-21 21:50:24 +0200
commite23bb04b0c938588eae41b7f4712b722290ed2b8 (patch)
tree024a12665cf2d599a175be5b5a29d61769dc4e84 /kernel/bpf/sysfs_btf.c
parenttools/bpftool: Support passing BPFTOOL_VERSION to make (diff)
downloadlinux-e23bb04b0c938588eae41b7f4712b722290ed2b8.tar.xz
linux-e23bb04b0c938588eae41b7f4712b722290ed2b8.zip
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/bpf/sysfs_btf.c')
-rw-r--r--kernel/bpf/sysfs_btf.c6
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);
}