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drivers/base: fix userspace break from using bin_attributes for cpumap and cpulist
Using bin_attributes with a 0 size causes fstat and friends to return that 0 size. This breaks userspace code that retrieves the size before reading the file. Rather than reverting75bd50fa84("drivers/base/node.c: use bin_attribute to break the size limitation of cpumap ABI") let's put in a size value at compile time. For cpulist the maximum size is on the order of NR_CPUS * (ceil(log10(NR_CPUS)) + 1)/2 which for 8192 is 20480 (8192 * 5)/2. In order to get near that you'd need a system with every other CPU on one node. For example: (0,2,4,8, ... ). To simplify the math and support larger NR_CPUS in the future we are using (NR_CPUS * 7)/2. We also set it to a min of PAGE_SIZE to retain the older behavior for smaller NR_CPUS. The cpumap file the size works out to be NR_CPUS/4 + NR_CPUS/32 - 1 (or NR_CPUS * 9/32 - 1) including the ","s. Add a set of macros for these values to cpumask.h so they can be used in multiple places. Apply these to the handful of such files in drivers/base/topology.c as well as node.c. As an example, on an 80 cpu 4-node system (NR_CPUS == 8192): before: -r--r--r--. 1 root root 0 Jul 12 14:08 system/node/node0/cpulist -r--r--r--. 1 root root 0 Jul 11 17:25 system/node/node0/cpumap after: -r--r--r--. 1 root root 28672 Jul 13 11:32 system/node/node0/cpulist -r--r--r--. 1 root root 4096 Jul 13 11:31 system/node/node0/cpumap CONFIG_NR_CPUS = 16384 -r--r--r--. 1 root root 57344 Jul 13 14:03 system/node/node0/cpulist -r--r--r--. 1 root root 4607 Jul 13 14:02 system/node/node0/cpumap The actual number of cpus doesn't matter for the reported size since they are based on NR_CPUS. Fixes:75bd50fa84("drivers/base/node.c: use bin_attribute to break the size limitation of cpumap ABI") Fixes:bb9ec13d15("topology: use bin_attribute to break the size limitation of cpumap ABI") Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: Yury Norov <yury.norov@gmail.com> Cc: stable@vger.kernel.org Acked-by: Yury Norov <yury.norov@gmail.com> (for include/linux/cpumask.h) Signed-off-by: Phil Auld <pauld@redhat.com> Link: https://lore.kernel.org/r/20220715134924.3466194-1-pauld@redhat.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Phil Auld
Greg Kroah-Hartman
parent
4a4e8f7f62
commit
7ee951acd3
@ -45,7 +45,7 @@ static inline ssize_t cpumap_read(struct file *file, struct kobject *kobj,
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return n;
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}
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static BIN_ATTR_RO(cpumap, 0);
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static BIN_ATTR_RO(cpumap, CPUMAP_FILE_MAX_BYTES);
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static inline ssize_t cpulist_read(struct file *file, struct kobject *kobj,
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struct bin_attribute *attr, char *buf,
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@ -66,7 +66,7 @@ static inline ssize_t cpulist_read(struct file *file, struct kobject *kobj,
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return n;
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}
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static BIN_ATTR_RO(cpulist, 0);
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static BIN_ATTR_RO(cpulist, CPULIST_FILE_MAX_BYTES);
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/**
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* struct node_access_nodes - Access class device to hold user visible
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@ -62,47 +62,47 @@ define_id_show_func(ppin, "0x%llx");
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static DEVICE_ATTR_ADMIN_RO(ppin);
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define_siblings_read_func(thread_siblings, sibling_cpumask);
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static BIN_ATTR_RO(thread_siblings, 0);
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static BIN_ATTR_RO(thread_siblings_list, 0);
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static BIN_ATTR_RO(thread_siblings, CPUMAP_FILE_MAX_BYTES);
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static BIN_ATTR_RO(thread_siblings_list, CPULIST_FILE_MAX_BYTES);
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define_siblings_read_func(core_cpus, sibling_cpumask);
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static BIN_ATTR_RO(core_cpus, 0);
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static BIN_ATTR_RO(core_cpus_list, 0);
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static BIN_ATTR_RO(core_cpus, CPUMAP_FILE_MAX_BYTES);
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static BIN_ATTR_RO(core_cpus_list, CPULIST_FILE_MAX_BYTES);
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define_siblings_read_func(core_siblings, core_cpumask);
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static BIN_ATTR_RO(core_siblings, 0);
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static BIN_ATTR_RO(core_siblings_list, 0);
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static BIN_ATTR_RO(core_siblings, CPUMAP_FILE_MAX_BYTES);
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static BIN_ATTR_RO(core_siblings_list, CPULIST_FILE_MAX_BYTES);
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#ifdef TOPOLOGY_CLUSTER_SYSFS
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define_siblings_read_func(cluster_cpus, cluster_cpumask);
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static BIN_ATTR_RO(cluster_cpus, 0);
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static BIN_ATTR_RO(cluster_cpus_list, 0);
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static BIN_ATTR_RO(cluster_cpus, CPUMAP_FILE_MAX_BYTES);
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static BIN_ATTR_RO(cluster_cpus_list, CPULIST_FILE_MAX_BYTES);
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#endif
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#ifdef TOPOLOGY_DIE_SYSFS
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define_siblings_read_func(die_cpus, die_cpumask);
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static BIN_ATTR_RO(die_cpus, 0);
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static BIN_ATTR_RO(die_cpus_list, 0);
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static BIN_ATTR_RO(die_cpus, CPUMAP_FILE_MAX_BYTES);
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static BIN_ATTR_RO(die_cpus_list, CPULIST_FILE_MAX_BYTES);
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#endif
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define_siblings_read_func(package_cpus, core_cpumask);
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static BIN_ATTR_RO(package_cpus, 0);
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static BIN_ATTR_RO(package_cpus_list, 0);
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static BIN_ATTR_RO(package_cpus, CPUMAP_FILE_MAX_BYTES);
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static BIN_ATTR_RO(package_cpus_list, CPULIST_FILE_MAX_BYTES);
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#ifdef TOPOLOGY_BOOK_SYSFS
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define_id_show_func(book_id, "%d");
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static DEVICE_ATTR_RO(book_id);
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define_siblings_read_func(book_siblings, book_cpumask);
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static BIN_ATTR_RO(book_siblings, 0);
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static BIN_ATTR_RO(book_siblings_list, 0);
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static BIN_ATTR_RO(book_siblings, CPUMAP_FILE_MAX_BYTES);
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static BIN_ATTR_RO(book_siblings_list, CPULIST_FILE_MAX_BYTES);
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#endif
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#ifdef TOPOLOGY_DRAWER_SYSFS
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define_id_show_func(drawer_id, "%d");
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static DEVICE_ATTR_RO(drawer_id);
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define_siblings_read_func(drawer_siblings, drawer_cpumask);
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static BIN_ATTR_RO(drawer_siblings, 0);
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static BIN_ATTR_RO(drawer_siblings_list, 0);
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static BIN_ATTR_RO(drawer_siblings, CPUMAP_FILE_MAX_BYTES);
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static BIN_ATTR_RO(drawer_siblings_list, CPULIST_FILE_MAX_BYTES);
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#endif
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static struct bin_attribute *bin_attrs[] = {
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@ -1071,4 +1071,22 @@ cpumap_print_list_to_buf(char *buf, const struct cpumask *mask,
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[0] = 1UL \
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} }
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/*
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* Provide a valid theoretical max size for cpumap and cpulist sysfs files
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* to avoid breaking userspace which may allocate a buffer based on the size
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* reported by e.g. fstat.
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*
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* for cpumap NR_CPUS * 9/32 - 1 should be an exact length.
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*
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* For cpulist 7 is (ceil(log10(NR_CPUS)) + 1) allowing for NR_CPUS to be up
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* to 2 orders of magnitude larger than 8192. And then we divide by 2 to
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* cover a worst-case of every other cpu being on one of two nodes for a
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* very large NR_CPUS.
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*
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* Use PAGE_SIZE as a minimum for smaller configurations.
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*/
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#define CPUMAP_FILE_MAX_BYTES ((((NR_CPUS * 9)/32 - 1) > PAGE_SIZE) \
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? (NR_CPUS * 9)/32 - 1 : PAGE_SIZE)
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#define CPULIST_FILE_MAX_BYTES (((NR_CPUS * 7)/2 > PAGE_SIZE) ? (NR_CPUS * 7)/2 : PAGE_SIZE)
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#endif /* __LINUX_CPUMASK_H */
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