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Smith" , Anthony PERARD , Andrew Cooper , Michal Orzel , Julien Grall , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Stefano Stabellini , xen-devel@lists.xenproject.org References: <20241213162421.16782-1-jgross@suse.com> <20241213162421.16782-6-jgross@suse.com> <7061e31b-2d61-40fd-b2e9-528c4faf41f9@suse.com> Content-Language: en-US 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: <7061e31b-2d61-40fd-b2e9-528c4faf41f9@suse.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 16.12.2024 16:03, Juergen Gross wrote: > On 16.12.24 11:41, Jan Beulich wrote: >> On 13.12.2024 17:24, Juergen Gross wrote: >>> --- a/xen/common/domain.c >>> +++ b/xen/common/domain.c >>> @@ -193,6 +193,57 @@ static void domain_changed_state(const struct domain *d) >>> spin_unlock(&dom_state_changed_lock); >>> } >>> >>> +static void set_domain_state_info(struct xen_domctl_get_domain_state *info, >>> + const struct domain *d) >>> +{ >>> + info->state = XEN_DOMCTL_GETDOMSTATE_STATE_EXIST; >>> + if ( d->is_shut_down ) >>> + info->state |= XEN_DOMCTL_GETDOMSTATE_STATE_SHUTDOWN; >>> + if ( d->is_dying == DOMDYING_dying ) >>> + info->state |= XEN_DOMCTL_GETDOMSTATE_STATE_DYING; >>> + if ( d->is_dying == DOMDYING_dead ) >>> + info->state |= XEN_DOMCTL_GETDOMSTATE_STATE_DEAD; >>> + info->unique_id = d->unique_id; >>> +} >>> + >>> +int get_domain_state(struct xen_domctl_get_domain_state *info, struct domain *d, >>> + domid_t *domid) >>> +{ >>> + unsigned int dom; >>> + >>> + if ( info->pad0 || info->pad1 ) >>> + return -EINVAL; >>> + >>> + if ( d ) >>> + { >>> + set_domain_state_info(info, d); >>> + >>> + return 0; >>> + } >>> + >>> + while ( (dom = find_first_bit(dom_state_changed, DOMID_MASK + 1)) < >>> + DOMID_FIRST_RESERVED ) >>> + { >>> + if ( test_and_clear_bit(dom, dom_state_changed) ) >> >> For these two accesses to dom_state_changed don't you need to hold the >> lock patch 4 introduces? Also didn't you say you'd constrain the new >> sub-op to the sole domain having VIRQ_DOM_EXEC bound (which, ftaod, >> isn't enough to eliminate the race)? > > Just to be more specific regarding the race: I guess you mean that a domain > having registered for the VIRQ doesn't mean the calling component being in > that domain really is the one associated with the VIRQ. > > While being true, even today it is possible for one dom0 user process to > "steal" a VIRQ from another process by using dirty tricks via the privcmd > driver. > > In the end a process having the access rights to use the privcmd driver must > be trusted to not disturb other processes with the same rights. Of course, but that's not exactly what I was getting at. I was trying to point out that the vIRQ check alone is still insufficient to avoid potential crashes here, by one vCPU calling here while another unbinds the vIRQ. Taking the lock is required for Xen's safety; checking the vIRQ is bound is an extra policy enforcement. Jan