s390/qeth: validate user buffer length in SNMP and ARP query ioctls

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commit d141f087b1 upstream.

qeth_snmp_command() and qeth_l3_arp_query() allocate a buffer sized by
a user-supplied length (udata_len) without checking a lower bound, then
set udata_offset to a fixed non-zero value and pass both to a reply
callback. The callback bounds-checks the copy with

        if ((udata_len - udata_offset) < len)

Both fields are u32, so a udata_len smaller than udata_offset makes the
subtraction wrap and the check pass, and the following memcpy() writes
past the allocation. A udata_len of 0 also yields ZERO_SIZE_PTR from
kzalloc(), which the existing NULL check does not catch.

Reject buffers smaller than udata_offset before allocating, so the
callback subtraction can no longer underflow.

Fixes: 4a71df5004 ("qeth: new qeth device driver")
Cc: stable@vger.kernel.org
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: Hidayath Khan <hidayath@linux.ibm.com>
Reviewed-by: Joe Damato <joe@dama.to>
Link: https://patch.msgid.link/20260730142216.218309-1-hidayath@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

Hidayath Khan 2026-07-30 16:22:16 +02:00 • committed by Greg Kroah-Hartman

parent b125609081

commit 46443eadde

2 changed files with 8 additions and 0 deletions

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3

drivers/s390/net/qeth_core_main.c

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5

drivers/s390/net/qeth_l3_main.c

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