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libbpf: btf_dump_type_data_check_overflow needs to consider BTF_MEMBER_BITFIELD_SIZE

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The btf_dump/struct_data selftest is failing with:

  [...]
  test_btf_dump_struct_data:FAIL:unexpected return value dumping fs_context unexpected unexpected return value dumping fs_context: actual -7 != expected 264
  [...]

The reason is in btf_dump_type_data_check_overflow(). It does not use
BTF_MEMBER_BITFIELD_SIZE from the struct's member (btf_member). Instead,
it is using the enum size which is 4. It had been working till the recent
commit 4e04143c86 ("fs_context: drop the unused lsm_flags member")
removed an integer member which also removed the 4 bytes padding at the
end of the fs_context. Missing this 4 bytes padding exposed this bug. In
particular, when btf_dump_type_data_check_overflow() reaches the member
'phase', -E2BIG is returned.

The fix is to pass bit_sz to btf_dump_type_data_check_overflow(). In
btf_dump_type_data_check_overflow(), it does a different size check when
bit_sz is not zero.

The current fs_context:

[3600] ENUM 'fs_context_purpose' encoding=UNSIGNED size=4 vlen=3
	'FS_CONTEXT_FOR_MOUNT' val=0
	'FS_CONTEXT_FOR_SUBMOUNT' val=1
	'FS_CONTEXT_FOR_RECONFIGURE' val=2
[3601] ENUM 'fs_context_phase' encoding=UNSIGNED size=4 vlen=7
	'FS_CONTEXT_CREATE_PARAMS' val=0
	'FS_CONTEXT_CREATING' val=1
	'FS_CONTEXT_AWAITING_MOUNT' val=2
	'FS_CONTEXT_AWAITING_RECONF' val=3
	'FS_CONTEXT_RECONF_PARAMS' val=4
	'FS_CONTEXT_RECONFIGURING' val=5
	'FS_CONTEXT_FAILED' val=6
[3602] STRUCT 'fs_context' size=264 vlen=21
	'ops' type_id=3603 bits_offset=0
	'uapi_mutex' type_id=235 bits_offset=64
	'fs_type' type_id=872 bits_offset=1216
	'fs_private' type_id=21 bits_offset=1280
	'sget_key' type_id=21 bits_offset=1344
	'root' type_id=781 bits_offset=1408
	'user_ns' type_id=251 bits_offset=1472
	'net_ns' type_id=984 bits_offset=1536
	'cred' type_id=1785 bits_offset=1600
	'log' type_id=3621 bits_offset=1664
	'source' type_id=42 bits_offset=1792
	'security' type_id=21 bits_offset=1856
	's_fs_info' type_id=21 bits_offset=1920
	'sb_flags' type_id=20 bits_offset=1984
	'sb_flags_mask' type_id=20 bits_offset=2016
	's_iflags' type_id=20 bits_offset=2048
	'purpose' type_id=3600 bits_offset=2080 bitfield_size=8
	'phase' type_id=3601 bits_offset=2088 bitfield_size=8
	'need_free' type_id=67 bits_offset=2096 bitfield_size=1
	'global' type_id=67 bits_offset=2097 bitfield_size=1
	'oldapi' type_id=67 bits_offset=2098 bitfield_size=1

Fixes: 920d16af9b ("libbpf: BTF dumper support for typed data")
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20230428013638.1581263-1-martin.lau@linux.dev
This commit is contained in:
Martin KaFai Lau 2023-04-27 18:36:38 -07:00 committed by Daniel Borkmann
parent 31f4f810d5
commit c39028b333
1 changed files with 19 additions and 3 deletions
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22
tools/lib/bpf/btf_dump.c
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@ -2250,9 +2250,25 @@ static int btf_dump_type_data_check_overflow(struct btf_dump *d,
const struct btf_type *t,
__u32 id,
const void *data,
__u8 bits_offset)
__u8 bits_offset,
__u8 bit_sz)
{
__s64 size = btf__resolve_size(d->btf, id);
__s64 size;
if (bit_sz) {
/* bits_offset is at most 7. bit_sz is at most 128. */
__u8 nr_bytes = (bits_offset + bit_sz + 7) / 8;
/* When bit_sz is non zero, it is called from
* btf_dump_struct_data() where it only cares about
* negative error value.
* Return nr_bytes in success case to make it
* consistent as the regular integer case below.
*/
return data + nr_bytes > d->typed_dump->data_end ? -E2BIG : nr_bytes;
}
size = btf__resolve_size(d->btf, id);
if (size < 0 || size >= INT_MAX) {
pr_warn("unexpected size [%zu] for id [%u]\n",
@ -2407,7 +2423,7 @@ static int btf_dump_dump_type_data(struct btf_dump *d,
{
int size, err = 0;
size = btf_dump_type_data_check_overflow(d, t, id, data, bits_offset);
size = btf_dump_type_data_check_overflow(d, t, id, data, bits_offset, bit_sz);
if (size < 0)
return size;
err = btf_dump_type_data_check_zero(d, t, id, data, bits_offset, bit_sz);