[ Upstream commit aa4d540b41 ]
GCC-13 (and Clang)[1] does not like to access a partially allocated
object, since it cannot reason about it for bounds checking.
In this case 140 bytes are allocated for an object of type struct
ib_umad_packet:
packet = kzalloc(sizeof(*packet) + IB_MGMT_RMPP_HDR, GFP_KERNEL);
However, notice that sizeof(*packet) is only 104 bytes:
struct ib_umad_packet {
struct ib_mad_send_buf * msg; /* 0 8 */
struct ib_mad_recv_wc * recv_wc; /* 8 8 */
struct list_head list; /* 16 16 */
int length; /* 32 4 */
/* XXX 4 bytes hole, try to pack */
struct ib_user_mad mad __attribute__((__aligned__(8))); /* 40 64 */
/* size: 104, cachelines: 2, members: 5 */
/* sum members: 100, holes: 1, sum holes: 4 */
/* forced alignments: 1, forced holes: 1, sum forced holes: 4 */
/* last cacheline: 40 bytes */
} __attribute__((__aligned__(8)));
and 36 bytes extra bytes are allocated for a flexible-array member in
struct ib_user_mad:
include/rdma/ib_mad.h:
120 enum {
...
123 IB_MGMT_RMPP_HDR = 36,
... }
struct ib_user_mad {
struct ib_user_mad_hdr hdr; /* 0 64 */
/* --- cacheline 1 boundary (64 bytes) --- */
__u64 data[] __attribute__((__aligned__(8))); /* 64 0 */
/* size: 64, cachelines: 1, members: 2 */
/* forced alignments: 1 */
} __attribute__((__aligned__(8)));
So we have sizeof(*packet) + IB_MGMT_RMPP_HDR == 140 bytes
Then the address of the flex-array member (for which only 36 bytes were
allocated) is casted and copied into a pointer to struct ib_rmpp_mad,
which, in turn, is of size 256 bytes:
rmpp_mad = (struct ib_rmpp_mad *) packet->mad.data;
struct ib_rmpp_mad {
struct ib_mad_hdr mad_hdr; /* 0 24 */
struct ib_rmpp_hdr rmpp_hdr; /* 24 12 */
u8 data[220]; /* 36 220 */
/* size: 256, cachelines: 4, members: 3 */
};
The thing is that those 36 bytes allocated for flex-array member data
in struct ib_user_mad onlly account for the size of both struct ib_mad_hdr
and struct ib_rmpp_hdr, but nothing is left for array u8 data[220].
So, the compiler is legitimately complaining about accessing an object
for which not enough memory was allocated.
Apparently, the only members of struct ib_rmpp_mad that are relevant
(that are actually being used) in function ib_umad_write() are mad_hdr
and rmpp_hdr. So, instead of casting packet->mad.data to
(struct ib_rmpp_mad *) create a new structure
struct ib_rmpp_mad_hdr {
struct ib_mad_hdr mad_hdr;
struct ib_rmpp_hdr rmpp_hdr;
} __packed;
and cast packet->mad.data to (struct ib_rmpp_mad_hdr *).
Notice that
IB_MGMT_RMPP_HDR == sizeof(struct ib_rmpp_mad_hdr) == 36 bytes
Refactor the rest of the code, accordingly.
Fix the following warnings seen under GCC-13 and -Warray-bounds:
drivers/infiniband/core/user_mad.c:564:50: warning: array subscript ‘struct ib_rmpp_mad[0]’ is partly outside array bounds of ‘unsigned char[140]’ [-Warray-bounds=]
drivers/infiniband/core/user_mad.c:566:42: warning: array subscript ‘struct ib_rmpp_mad[0]’ is partly outside array bounds of ‘unsigned char[140]’ [-Warray-bounds=]
drivers/infiniband/core/user_mad.c:618:25: warning: array subscript ‘struct ib_rmpp_mad[0]’ is partly outside array bounds of ‘unsigned char[140]’ [-Warray-bounds=]
drivers/infiniband/core/user_mad.c:622:44: warning: array subscript ‘struct ib_rmpp_mad[0]’ is partly outside array bounds of ‘unsigned char[140]’ [-Warray-bounds=]
Link: https://github.com/KSPP/linux/issues/273
Link: https://godbolt.org/z/oYWaGM4Yb [1]
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/ZBpB91qQcB10m3Fw@work
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
036e02dfd5