From 20eb87c94b862d82c5c5eb279a2dc085045059b5 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Tue, 7 Nov 2017 16:44:36 -0500 Subject: [PATCH] Fix: lttng_kvmalloc helper NULL pointer OOPS The static function __vmalloc_node is not visible by KALLSYMS_ALL on at least some kernels, which leads to a call to a NULL function when trying to perform allocation of lttng buffer memory under memory fragmentation conditions (kmalloc_node failure). Use __vmalloc_node_range instead, and check that the returned pointer is non-NULL to ensure this type of failure does not happen in any condition. Fallback to __vmalloc(), even though it is not NUMA-aware, in case we fail to find __vmalloc_node_range, and print an explicit warning to the user console about the need to enable KALLSYMS_ALL. This affects kernels < 4.12. Later kernels provide kvmalloc(), which we use. Signed-off-by: Mathieu Desnoyers --- wrapper/vmalloc.h | 63 ++++++++++++++++++++++------------------------- 1 file changed, 29 insertions(+), 34 deletions(-) diff --git a/wrapper/vmalloc.h b/wrapper/vmalloc.h index e117584f..b4d79540 100644 --- a/wrapper/vmalloc.h +++ b/wrapper/vmalloc.h @@ -107,32 +107,40 @@ void lttng_kvfree(const void *addr) #include +static inline +void print_vmalloc_node_range_warning(void) +{ + printk_once(KERN_WARNING "LTTng: __vmalloc_node_range symbol lookup failed.\n"); + printk_once(KERN_WARNING "Tracer performance will be degraded on NUMA systems.\n"); + printk_once(KERN_WARNING "Please rebuild your kernel with CONFIG_KALLSYMS enabled.\n"); +} + /* * kallsyms wrapper of __vmalloc_node with a fallback to kmalloc_node. */ static inline -void *__lttng_vmalloc_node_fallback(unsigned long size, unsigned long align, - gfp_t gfp_mask, pgprot_t prot, int node, void *caller) +void *__lttng_vmalloc_node_range(unsigned long size, unsigned long align, + unsigned long start, unsigned long end, gfp_t gfp_mask, + pgprot_t prot, unsigned long vm_flags, int node, + const void *caller) { - void *ret; - #ifdef CONFIG_KALLSYMS /* - * If we have KALLSYMS, get * __vmalloc_node which is not exported. + * If we have KALLSYMS, get * __vmalloc_node_range which is not exported. */ - void *(*lttng__vmalloc_node)(unsigned long size, unsigned long align, - gfp_t gfp_mask, pgprot_t prot, int node, void *caller); - - lttng__vmalloc_node = (void *) kallsyms_lookup_funcptr("__vmalloc_node"); - ret = lttng__vmalloc_node(size, align, gfp_mask, prot, node, caller); -#else - /* - * If we don't have KALLSYMS, fallback to kmalloc_node. - */ - ret = kmalloc_node(size, flags, node); + void *(*lttng__vmalloc_node_range)(unsigned long size, unsigned long align, + unsigned long start, unsigned long end, gfp_t gfp_mask, + pgprot_t prot, unsigned long vm_flags, int node, + const void *caller); + + lttng__vmalloc_node_range = (void *) kallsyms_lookup_funcptr("__vmalloc_node_range"); + if (lttng__vmalloc_node_range) + return lttng__vmalloc_node_range(size, align, start, end, gfp_mask, prot, + vm_flags, node, caller); #endif - - return ret; + if (node != NUMA_NO_NODE) + print_vmalloc_node_range_warning(); + return __vmalloc(size, gfp_mask, prot); } /** @@ -170,23 +178,10 @@ void *lttng_kvmalloc_node(unsigned long size, gfp_t flags, int node) */ ret = kmalloc_node(size, flags | __GFP_NOWARN | __GFP_NORETRY, node); if (!ret) { - if (node == NUMA_NO_NODE) { - /* - * If no node was specified, use __vmalloc which is - * always exported. - */ - ret = __vmalloc(size, flags | __GFP_HIGHMEM, PAGE_KERNEL); - } else { - /* - * Otherwise, we need to select a node but __vmalloc_node - * is not exported, use this fallback wrapper which uses - * kallsyms if available or falls back to kmalloc_node. - */ - ret = __lttng_vmalloc_node_fallback(size, 1, - flags | __GFP_HIGHMEM, PAGE_KERNEL, node, - __builtin_return_address(0)); - } - + ret = __lttng_vmalloc_node_range(size, 1, + VMALLOC_START, VMALLOC_END, + flags | __GFP_HIGHMEM, PAGE_KERNEL, 0, + node, __builtin_return_address(0)); /* * Make sure we don't trigger recursive page faults in the * tracing fast path. -- 2.34.1