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Wed, 24 Jun 2026 06:12:50 -0700 (PDT) Message-ID: <0f71d767-16a7-4518-a692-ea9b8d482e3d@suse.com> Date: Wed, 24 Jun 2026 15:12:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: New Defects reported by Coverity Scan for XenProject To: "xen-devel@lists.xenproject.org" References: <6a3bce99e5494_767442bc3001679a440720@prd-scan-dashboard-0.mail> Content-Language: en-US Cc: Andrew Cooper , Julien Grall , Stefano Stabellini , Anthony PERARD , Michal Orzel , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= From: Jan Beulich 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 In-Reply-To: <6a3bce99e5494_767442bc3001679a440720@prd-scan-dashboard-0.mail> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-purgate-ID: tlsNG-42698a/1782306771-A653B220-5DAE36D7/0/0 X-purgate-type: clean X-purgate-size: 1402 On 24.06.2026 14:33, scan-admin@coverity.com wrote: > ** CID 1695360: Integer handling issues (BAD_SHIFT) > /xen/common/numa.c: 483 in extract_lsb_from_nodes() > > > _____________________________________________________________________________________________ > *** CID 1695360: Integer handling issues (BAD_SHIFT) > /xen/common/numa.c: 483 in extract_lsb_from_nodes() > 477 > 478 if ( nodes_used <= 1 ) > 479 i = min(PADDR_BITS, BITS_PER_LONG - 1); > 480 else > 481 i = find_first_bit(&bitfield, sizeof(unsigned long) * 8); > 482 >>>> CID 1695360: Integer handling issues (BAD_SHIFT) >>>> In expression "memtop - 1UL >> i", right shifting by more than 63 bits has undefined behavior. The shift amount, "i", is 64. > 483 memnodemapsize = ((memtop - 1) >> i) + 1; > 484 > 485 return i; > 486 } Without contextual knowledge I think the complaint is reasonable. However, for nodes_used to be greater than 1, we will need to have ORed spdx into bitfield on an iteration later than the 1st one. Yet only on the 1st iteration can spdx be 0 (or, if nodes[] wasn't sorted, only on one of the at least two involved iterations). Hence bitfield isn't going to be 0, and thus find_first_bit() is going to return a value lower than BITS_PER_LONG. Jan