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Fri, 25 Apr 2025 07:57:19 -0700 (PDT) Message-ID: <8e31896e-3603-4969-af7c-3175ceacff55@suse.com> Date: Fri, 25 Apr 2025 16:57:18 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Jan Beulich Subject: [PATCH v2] x86: constrain sub-page access length in mmio_ro_emulated_write() To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Marek Marczykowski Content-Language: en-US Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @suse.com) X-ZM-MESSAGEID: 1745593062201019100 Content-Type: text/plain; charset="utf-8" Without doing so we could trigger the ASSERT_UNREACHABLE() in subpage_mmio_write_emulate(). A comment there actually says this validation would already have been done ... Fixes: 8847d6e23f97 ("x86/mm: add API for marking only part of a MMIO page = read only") Signed-off-by: Jan Beulich Reviewed-by: Jason Andryuk Reviewed-by: Roger Pau Monn=C3=A9 --- v2: Emit a warning message otherwise. --- a/xen/arch/x86/mm.c +++ b/xen/arch/x86/mm.c @@ -5195,8 +5195,13 @@ int cf_check mmio_ro_emulated_write( return X86EMUL_UNHANDLEABLE; } =20 - subpage_mmio_write_emulate(mmio_ro_ctxt->mfn, PAGE_OFFSET(offset), - p_data, bytes); + if ( bytes <=3D 8 ) + subpage_mmio_write_emulate(mmio_ro_ctxt->mfn, PAGE_OFFSET(offset), + p_data, bytes); + else if ( subpage_mmio_find_page(mmio_ro_ctxt->mfn) ) + gprintk(XENLOG_WARNING, + "unsupported %u-byte write to R/O MMIO 0x%"PRI_mfn"%03lx\n= ", + bytes, mfn_x(mmio_ro_ctxt->mfn), PAGE_OFFSET(offset)); =20 return X86EMUL_OKAY; }