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Tue, 22 Jul 2025 08:29:05 -0400 (EDT) From: Michael Zhivich To: , CC: , , , , , Michael Zhivich Subject: [PATCH v2] x86/bugs: Fix use of possibly uninit value in amd_check_tsa_microcode() Date: Tue, 22 Jul 2025 08:28:44 -0400 Message-ID: <20250722122844.2199661-1-mzhivich@akamai.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-07-22_02,2025-07-21_02,2025-03-28_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 bulkscore=0 malwarescore=0 suspectscore=0 mlxscore=0 spamscore=0 phishscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2505160000 definitions=main-2507220101 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNzIyMDEwMiBTYWx0ZWRfX8wo69AXnXZdu HIjxXgqXVGoc3VZcxhXGIGTQ8URhBpcvUIdsx20z3vY/YDi6A7RS4ZVd5Opf8rQrNEEbYpfu/6i WHRi55s5WfPOjuO2/7vveQp4Y4krsO16vKcQaNFrKlVVl5mqrG8ys4d/LRPyVD48R8dtJ+Cy+J+ ofgI9GHl8f1dQ5sSRr4/OxFgvtyY1jIVDkBlbyBaIjyQxgygEqYxOq083DqDe3AA8ojVU6A6sEx 2Co4ETAVmAxnKHiO6DOrO19ma7iov0lQXe6CNN73YDM371zjZ4K1SPZfVJZ1vHPTB0vzkK/7iA/ rlGVz+jCtm07QZxMONZrbEDCKrDKz3GVzMhzro6ZjAItVWNX+EoZ6YA00qDFUIYfxd8hgBNSJou v5cmsI0EhNUoeyFxVpkbpGzxqm5ebm+2ufC3iEiWuiY1AQXmwbOhM32U44s69aqnyxUkUr7s X-Proofpoint-GUID: kcexfW2z2x8Rgo-taRY0L8EXvUTwYDst X-Proofpoint-ORIG-GUID: kcexfW2z2x8Rgo-taRY0L8EXvUTwYDst X-Authority-Analysis: v=2.4 cv=H8Pbw/Yi c=1 sm=1 tr=0 ts=687f8413 cx=c_pps a=3lD5tZmBJQAvN++OlPJl4w==:117 a=3lD5tZmBJQAvN++OlPJl4w==:17 a=Wb1JkmetP80A:10 a=VwQbUJbxAAAA:8 a=X7Ea-ya5AAAA:8 a=pmTPSbCVOfBdVNymtuMA:9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-07-22_02,2025-07-21_02,2025-03-28_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 mlxlogscore=893 priorityscore=1501 impostorscore=0 lowpriorityscore=0 malwarescore=0 suspectscore=0 mlxscore=0 adultscore=0 phishscore=0 bulkscore=0 clxscore=1015 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505280000 definitions=main-2507220102 Content-Type: text/plain; charset="utf-8" For kernels compiled with CONFIG_INIT_STACK_NONE=3Dy, the value of __reserv= ed field in zen_patch_rev union on the stack may be garbage. If so, it will prevent correct microcode check when consulting p.ucode_rev, resulting in incorrect mitigation selection. Cc: Signed-off-by: Michael Zhivich Fixes: 7a0395f6607a5 ("x86/bugs: Add a Transient Scheduler Attacks mitigati= on") Acked-by: Borislav Petkov (AMD) --- Changes in v2: - Rework patch per feedback - Add Cc: stable arch/x86/kernel/cpu/amd.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index efd42ee9d1cc..289ff197b1b3 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -378,6 +378,8 @@ static bool amd_check_tsa_microcode(void) p.model =3D c->x86_model; p.ext_model =3D c->x86_model >> 4; p.stepping =3D c->x86_stepping; + /* reserved bits are expected to be 0 in test below */ + p.__reserved =3D 0; =20 if (cpu_has(c, X86_FEATURE_ZEN3) || cpu_has(c, X86_FEATURE_ZEN4)) { --=20 2.34.1