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RDMA/umad: Reject negative data_len in ib_umad_write

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ib_umad_write computes data_len from user-controlled count and the
MAD header sizes. With a mismatched user MAD header size and RMPP
header length, data_len can become negative and reach ib_create_send_mad().
This can make the padding calculation exceed the segment size and trigger
an out-of-bounds memset in alloc_send_rmpp_list().

Add an explicit check to reject negative data_len before creating the
send buffer.

KASAN splat:
[  211.363464] BUG: KASAN: slab-out-of-bounds in ib_create_send_mad+0xa01/0x11b0
[  211.364077] Write of size 220 at addr ffff88800c3fa1f8 by task spray_thread/102
[  211.365867] ib_create_send_mad+0xa01/0x11b0
[  211.365887] ib_umad_write+0x853/0x1c80

Fixes: 2be8e3ee8e ("IB/umad: Add P_Key index support")
Signed-off-by: YunJe Shin <ioerts@kookmin.ac.kr>
Link: https://patch.msgid.link/20260203100628.1215408-1-ioerts@kookmin.ac.kr
Signed-off-by: Leon Romanovsky <leon@kernel.org>
This commit is contained in:
YunJe Shin 2026-02-03 19:06:21 +09:00 committed by Leon Romanovsky
parent 42e3aac65c
commit 5551b02fdb
1 changed files with 6 additions and 2 deletions
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8
drivers/infiniband/core/user_mad.c
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@ -514,7 +514,8 @@ static ssize_t ib_umad_write(struct file *filp, const char __user *buf,
struct rdma_ah_attr ah_attr;
struct ib_ah *ah;
__be64 *tid;
int ret, data_len, hdr_len, copy_offset, rmpp_active;
int ret, hdr_len, copy_offset, rmpp_active;
size_t data_len;
u8 base_version;
if (count < hdr_size(file) + IB_MGMT_RMPP_HDR)
@ -588,7 +589,10 @@ static ssize_t ib_umad_write(struct file *filp, const char __user *buf,
}
base_version = ((struct ib_mad_hdr *)&packet->mad.data)->base_version;
data_len = count - hdr_size(file) - hdr_len;
if (check_sub_overflow(count, hdr_size(file) + hdr_len, &data_len)) {
ret = -EINVAL;
goto err_ah;
}
packet->msg = ib_create_send_mad(agent,
be32_to_cpu(packet->mad.hdr.qpn),
packet->mad.hdr.pkey_index, rmpp_active,