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Mon, 15 Dec 2025 03:22:34 -0800 (PST) Message-ID: <7d254163-ac13-4c58-bcb5-aaff2e892e15@suse.com> Date: Mon, 15 Dec 2025 12:22:36 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , Julien Grall , Stefano Stabellini , Anthony PERARD , Michal Orzel , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= From: Jan Beulich Subject: [PATCH] memory: overlapping XENMAPSPACE_gmfn_range requests 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: 1765797794053158500 Content-Type: text/plain; charset="utf-8" Overlapping requests may need processing backwards, or else the intended effect wouldn't be achieved (and instead some pages would be moved more than once). Also covers XEN_DMOP_relocate_memory, where the potential issue was first noticed. Fixes: a04811a315e0 ("mm: New XENMEM space, XENMAPSPACE_gmfn_range") Reported-by: Andrew Cooper Signed-off-by: Jan Beulich --- Of course an alternative would be to simply reject overlapping requests. Then we should reject all overlaps though, I think. But since the code change didn't end up overly intrusive, I thought I would go the "fix it" route first. In-place moves (->idx =3D=3D ->gpfn) are effectively no-ops, but we don't l= ook to short-circuit them for XENMAPSPACE_gmfn, so they're not short-circuited here either. --- a/xen/common/memory.c +++ b/xen/common/memory.c @@ -849,7 +849,7 @@ int xenmem_add_to_physmap(struct domain unsigned int start) { unsigned int done =3D 0; - long rc =3D 0; + long rc =3D 0, adjust =3D 1; union add_to_physmap_extra extra =3D {}; struct page_info *pages[16]; =20 @@ -884,8 +884,25 @@ int xenmem_add_to_physmap(struct domain return -EOVERFLOW; } =20 - xatp->idx +=3D start; - xatp->gpfn +=3D start; + /* + * Overlapping ranges need processing backwards when destination is ab= ove + * source. + */ + if ( xatp->gpfn > xatp->idx && + unlikely(xatp->gpfn < xatp->idx + xatp->size) ) + { + adjust =3D -1; + + /* Both fields store "next item to process". */ + xatp->idx +=3D xatp->size - start - 1; + xatp->gpfn +=3D xatp->size - start - 1; + } + else + { + xatp->idx +=3D start; + xatp->gpfn +=3D start; + } + xatp->size -=3D start; =20 #ifdef CONFIG_HAS_PASSTHROUGH @@ -903,8 +920,8 @@ int xenmem_add_to_physmap(struct domain if ( rc < 0 ) break; =20 - xatp->idx++; - xatp->gpfn++; + xatp->idx +=3D adjust; + xatp->gpfn +=3D adjust; =20 if ( extra.ppage ) ++extra.ppage; @@ -927,7 +944,10 @@ int xenmem_add_to_physmap(struct domain =20 this_cpu(iommu_dont_flush_iotlb) =3D 0; =20 - ret =3D iommu_iotlb_flush(d, _dfn(xatp->idx - done), done, + if ( likely(adjust > 0) ) + adjust =3D done; + + ret =3D iommu_iotlb_flush(d, _dfn(xatp->idx - adjust), done, IOMMU_FLUSHF_modified); if ( unlikely(ret) && rc >=3D 0 ) rc =3D ret; @@ -941,7 +961,7 @@ int xenmem_add_to_physmap(struct domain for ( i =3D 0; i < done; ++i ) put_page(pages[i]); =20 - ret =3D iommu_iotlb_flush(d, _dfn(xatp->gpfn - done), done, + ret =3D iommu_iotlb_flush(d, _dfn(xatp->gpfn - adjust), done, IOMMU_FLUSHF_added | IOMMU_FLUSHF_modified= ); if ( unlikely(ret) && rc >=3D 0 ) rc =3D ret;