From: Martin KaFai Lau martin.lau@kernel.org
[ Upstream commit c39028b333f3a3a765c5c0b9726b8e38aedf0ba1 ]
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 4e04143c869c ("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: 920d16af9b42 ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- tools/lib/bpf/btf_dump.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c index 580985ee55458..4d9f30bf7f014 100644 --- a/tools/lib/bpf/btf_dump.c +++ b/tools/lib/bpf/btf_dump.c @@ -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);