Bug 2536408 (CVE-2026-90435)

Summary: CVE-2026-90435 kernel: RDMA/mlx5: Fix integer overflow of user QP buffer size
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's RDMA/mlx5 component. A local attacker could exploit an integer overflow vulnerability when processing user-supplied buffer size values. This flaw occurs because large user inputs can cause an integer overflow during buffer size calculation, leading to a smaller buffer being allocated than required. Consequently, this can result in a buffer overflow, potentially allowing for memory corruption.
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Description OSIDB Bzimport 2026-09-17 17:44:54 UTC 
In the Linux kernel, the following vulnerability has been resolved:

RDMA/mlx5: Fix integer overflow of user QP buffer size

set_user_buf_size() computes the QP buffer size by left-shifting the
user-supplied rq.wqe_cnt and rq.wqe_shift values as signed integers.
A sufficiently large rq.wqe_cnt causes signed integer overflow, which
is undefined behavior, and yields a small or negative buf_size, causing
ib_umem_get() to map a buffer smaller than the hardware will actually
write into.

Replace the shifts and addition with check_shl_overflow() and
check_add_overflow(), rejecting invalid user inputs.

Moreover, guard the identical shift computing qp->sq.offset in
_create_user_qp() before set_user_buf_size() is reached.
Comment 1 gkamathe 2026-09-20 07:31:43 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90435.mbox