From 23b5908b11b77ff8d7b8f7b8f11cbab2e1f4bfc2 Mon Sep 17 00:00:00 2001 From: Ricardo Neri Date: Wed, 27 Nov 2024 16:22:46 -0800 Subject: [PATCH] cacheinfo: Allocate memory during CPU hotplug if not done from the primary CPU commit b3fce429a1e030b50c1c91351d69b8667eef627b upstream. Commit 5944ce092b97 ("arch_topology: Build cacheinfo from primary CPU") adds functionality that architectures can use to optionally allocate and build cacheinfo early during boot. Commit 6539cffa9495 ("cacheinfo: Add arch specific early level initializer") lets secondary CPUs correct (and reallocate memory) cacheinfo data if needed. If the early build functionality is not used and cacheinfo does not need correction, memory for cacheinfo is never allocated. x86 does not use the early build functionality. Consequently, during the cacheinfo CPU hotplug callback, last_level_cache_is_valid() attempts to dereference a NULL pointer: BUG: kernel NULL pointer dereference, address: 0000000000000100 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not present page PGD 0 P4D 0 Oops: 0000 [#1] PREEPMT SMP NOPTI CPU: 0 PID 19 Comm: cpuhp/0 Not tainted 6.4.0-rc2 #1 RIP: 0010: last_level_cache_is_valid+0x95/0xe0a Allocate memory for cacheinfo during the cacheinfo CPU hotplug callback if not done earlier. Moreover, before determining the validity of the last-level cache info, ensure that it has been allocated. Simply checking for non-zero cache_leaves() is not sufficient, as some architectures (e.g., Intel processors) have non-zero cache_leaves() before allocation. Dereferencing NULL cacheinfo can occur in update_per_cpu_data_slice_size(). This function iterates over all online CPUs. However, a CPU may have come online recently, but its cacheinfo may not have been allocated yet. While here, remove an unnecessary indentation in allocate_cache_info(). [ bp: Massage. ] Fixes: 6539cffa9495 ("cacheinfo: Add arch specific early level initializer") Signed-off-by: Ricardo Neri Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Radu Rendec Reviewed-by: Nikolay Borisov Reviewed-by: Andreas Herrmann Reviewed-by: Sudeep Holla Cc: stable@vger.kernel.org # 6.3+ Link: https://lore.kernel.org/r/20241128002247.26726-2-ricardo.neri-calderon@linux.intel.com Signed-off-by: Greg Kroah-Hartman --- drivers/base/cacheinfo.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c index cbae8be1fe5200..b5715b8ded8974 100644 --- a/drivers/base/cacheinfo.c +++ b/drivers/base/cacheinfo.c @@ -58,7 +58,7 @@ bool last_level_cache_is_valid(unsigned int cpu) { struct cacheinfo *llc; - if (!cache_leaves(cpu)) + if (!cache_leaves(cpu) || !per_cpu_cacheinfo(cpu)) return false; llc = per_cpu_cacheinfo_idx(cpu, cache_leaves(cpu) - 1); @@ -478,11 +478,9 @@ int __weak populate_cache_leaves(unsigned int cpu) return -ENOENT; } -static inline -int allocate_cache_info(int cpu) +static inline int allocate_cache_info(int cpu) { - per_cpu_cacheinfo(cpu) = kcalloc(cache_leaves(cpu), - sizeof(struct cacheinfo), GFP_ATOMIC); + per_cpu_cacheinfo(cpu) = kcalloc(cache_leaves(cpu), sizeof(struct cacheinfo), GFP_ATOMIC); if (!per_cpu_cacheinfo(cpu)) { cache_leaves(cpu) = 0; return -ENOMEM; @@ -554,7 +552,11 @@ static inline int init_level_allocate_ci(unsigned int cpu) */ ci_cacheinfo(cpu)->early_ci_levels = false; - if (cache_leaves(cpu) <= early_leaves) + /* + * Some architectures (e.g., x86) do not use early initialization. + * Allocate memory now in such case. + */ + if (cache_leaves(cpu) <= early_leaves && per_cpu_cacheinfo(cpu)) return 0; kfree(per_cpu_cacheinfo(cpu));