CVE-2026-23243

In the Linux kernel, the following vulnerability has been resolved:

RDMA/umad: Reject negative datalen in ibumad_write

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

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 ibcreatesendmad+0xa01/0x11b0 [ 211.364077] Write of size 220 at addr ffff88800c3fa1f8 by task spraythread/102 [ 211.365867] ibcreatesendmad+0xa01/0x11b0 [ 211.365887] ibumad_write+0x853/0x1c80