The patch titled Subject: alloc_tag: allocate percpu counters for module tags dynamically has been added to the -mm mm-hotfixes-unstable branch. Its filename is alloc_tag-allocate-percpu-counters-for-module-tags-dynamically.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: Suren Baghdasaryan surenb@google.com Subject: alloc_tag: allocate percpu counters for module tags dynamically Date: Fri, 16 May 2025 17:07:39 -0700
When a module gets unloaded it checks whether any of its tags are still in use and if so, we keep the memory containing module's allocation tags alive until all tags are unused. However percpu counters referenced by the tags are freed by free_module(). This will lead to UAF if the memory allocated by a module is accessed after module was unloaded.
To fix this we allocate percpu counters for module allocation tags dynamically and we keep it alive for tags which are still in use after module unloading. This also removes the requirement of a larger PERCPU_MODULE_RESERVE when memory allocation profiling is enabled because percpu memory for counters does not need to be reserved anymore.
Link: https://lkml.kernel.org/r/20250517000739.5930-1-surenb@google.com Fixes: 0db6f8d7820a ("alloc_tag: load module tags into separate contiguous memory") Signed-off-by: Suren Baghdasaryan surenb@google.com Reported-by: David Wang 00107082@163.com Closes: https://lore.kernel.org/all/20250516131246.6244-1-00107082@163.com/ Tested-by: David Wang 00107082@163.com Cc: Christoph Lameter (Ampere) cl@gentwo.org Cc: Dennis Zhou dennis@kernel.org Cc: Kent Overstreet kent.overstreet@linux.dev Cc: Pasha Tatashin pasha.tatashin@soleen.com Cc: Tejun Heo tj@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
include/linux/alloc_tag.h | 12 ++++ include/linux/codetag.h | 8 +-- include/linux/percpu.h | 4 - lib/alloc_tag.c | 89 ++++++++++++++++++++++++++++-------- lib/codetag.c | 5 +- 5 files changed, 89 insertions(+), 29 deletions(-)
--- a/include/linux/alloc_tag.h~alloc_tag-allocate-percpu-counters-for-module-tags-dynamically +++ a/include/linux/alloc_tag.h @@ -104,6 +104,16 @@ DECLARE_PER_CPU(struct alloc_tag_counter
#else /* ARCH_NEEDS_WEAK_PER_CPU */
+#ifdef MODULE + +#define DEFINE_ALLOC_TAG(_alloc_tag) \ + static struct alloc_tag _alloc_tag __used __aligned(8) \ + __section(ALLOC_TAG_SECTION_NAME) = { \ + .ct = CODE_TAG_INIT, \ + .counters = NULL }; + +#else /* MODULE */ + #define DEFINE_ALLOC_TAG(_alloc_tag) \ static DEFINE_PER_CPU(struct alloc_tag_counters, _alloc_tag_cntr); \ static struct alloc_tag _alloc_tag __used __aligned(8) \ @@ -111,6 +121,8 @@ DECLARE_PER_CPU(struct alloc_tag_counter .ct = CODE_TAG_INIT, \ .counters = &_alloc_tag_cntr };
+#endif /* MODULE */ + #endif /* ARCH_NEEDS_WEAK_PER_CPU */
DECLARE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT, --- a/include/linux/codetag.h~alloc_tag-allocate-percpu-counters-for-module-tags-dynamically +++ a/include/linux/codetag.h @@ -36,10 +36,10 @@ union codetag_ref { struct codetag_type_desc { const char *section; size_t tag_size; - void (*module_load)(struct codetag_type *cttype, - struct codetag_module *cmod); - void (*module_unload)(struct codetag_type *cttype, - struct codetag_module *cmod); + void (*module_load)(struct module *mod, + struct codetag *start, struct codetag *end); + void (*module_unload)(struct module *mod, + struct codetag *start, struct codetag *end); #ifdef CONFIG_MODULES void (*module_replaced)(struct module *mod, struct module *new_mod); bool (*needs_section_mem)(struct module *mod, unsigned long size); --- a/include/linux/percpu.h~alloc_tag-allocate-percpu-counters-for-module-tags-dynamically +++ a/include/linux/percpu.h @@ -15,11 +15,7 @@
/* enough to cover all DEFINE_PER_CPUs in modules */ #ifdef CONFIG_MODULES -#ifdef CONFIG_MEM_ALLOC_PROFILING -#define PERCPU_MODULE_RESERVE (8 << 13) -#else #define PERCPU_MODULE_RESERVE (8 << 10) -#endif #else #define PERCPU_MODULE_RESERVE 0 #endif --- a/lib/alloc_tag.c~alloc_tag-allocate-percpu-counters-for-module-tags-dynamically +++ a/lib/alloc_tag.c @@ -350,18 +350,28 @@ static bool needs_section_mem(struct mod return size >= sizeof(struct alloc_tag); }
-static struct alloc_tag *find_used_tag(struct alloc_tag *from, struct alloc_tag *to) +static bool clean_unused_counters(struct alloc_tag *start_tag, + struct alloc_tag *end_tag) { - while (from <= to) { + struct alloc_tag *tag; + bool ret = true; + + for (tag = start_tag; tag <= end_tag; tag++) { struct alloc_tag_counters counter;
- counter = alloc_tag_read(from); - if (counter.bytes) - return from; - from++; + if (!tag->counters) + continue; + + counter = alloc_tag_read(tag); + if (!counter.bytes) { + free_percpu(tag->counters); + tag->counters = NULL; + } else { + ret = false; + } }
- return NULL; + return ret; }
/* Called with mod_area_mt locked */ @@ -371,12 +381,16 @@ static void clean_unused_module_areas_lo struct module *val;
mas_for_each(&mas, val, module_tags.size) { + struct alloc_tag *start_tag; + struct alloc_tag *end_tag; + if (val != &unloaded_mod) continue;
/* Release area if all tags are unused */ - if (!find_used_tag((struct alloc_tag *)(module_tags.start_addr + mas.index), - (struct alloc_tag *)(module_tags.start_addr + mas.last))) + start_tag = (struct alloc_tag *)(module_tags.start_addr + mas.index); + end_tag = (struct alloc_tag *)(module_tags.start_addr + mas.last); + if (clean_unused_counters(start_tag, end_tag)) mas_erase(&mas); } } @@ -561,7 +575,8 @@ unlock: static void release_module_tags(struct module *mod, bool used) { MA_STATE(mas, &mod_area_mt, module_tags.size, module_tags.size); - struct alloc_tag *tag; + struct alloc_tag *start_tag; + struct alloc_tag *end_tag; struct module *val;
mas_lock(&mas); @@ -575,15 +590,22 @@ static void release_module_tags(struct m if (!used) goto release_area;
- /* Find out if the area is used */ - tag = find_used_tag((struct alloc_tag *)(module_tags.start_addr + mas.index), - (struct alloc_tag *)(module_tags.start_addr + mas.last)); - if (tag) { - struct alloc_tag_counters counter = alloc_tag_read(tag); - - pr_info("%s:%u module %s func:%s has %llu allocated at module unload\n", - tag->ct.filename, tag->ct.lineno, tag->ct.modname, - tag->ct.function, counter.bytes); + start_tag = (struct alloc_tag *)(module_tags.start_addr + mas.index); + end_tag = (struct alloc_tag *)(module_tags.start_addr + mas.last); + if (!clean_unused_counters(start_tag, end_tag)) { + struct alloc_tag *tag; + + for (tag = start_tag; tag <= end_tag; tag++) { + struct alloc_tag_counters counter; + + if (!tag->counters) + continue; + + counter = alloc_tag_read(tag); + pr_info("%s:%u module %s func:%s has %llu allocated at module unload\n", + tag->ct.filename, tag->ct.lineno, tag->ct.modname, + tag->ct.function, counter.bytes); + } } else { used = false; } @@ -596,6 +618,34 @@ out: mas_unlock(&mas); }
+static void load_module(struct module *mod, struct codetag *start, struct codetag *stop) +{ + /* Allocate module alloc_tag percpu counters */ + struct alloc_tag *start_tag; + struct alloc_tag *stop_tag; + struct alloc_tag *tag; + + if (!mod) + return; + + start_tag = ct_to_alloc_tag(start); + stop_tag = ct_to_alloc_tag(stop); + for (tag = start_tag; tag < stop_tag; tag++) { + WARN_ON(tag->counters); + tag->counters = alloc_percpu(struct alloc_tag_counters); + if (!tag->counters) { + while (--tag >= start_tag) { + free_percpu(tag->counters); + tag->counters = NULL; + } + shutdown_mem_profiling(true); + pr_err("Failed to allocate memory for allocation tag percpu counters in the module %s. Memory allocation profiling is disabled!\n", + mod->name); + break; + } + } +} + static void replace_module(struct module *mod, struct module *new_mod) { MA_STATE(mas, &mod_area_mt, 0, module_tags.size); @@ -757,6 +807,7 @@ static int __init alloc_tag_init(void) .needs_section_mem = needs_section_mem, .alloc_section_mem = reserve_module_tags, .free_section_mem = release_module_tags, + .module_load = load_module, .module_replaced = replace_module, #endif }; --- a/lib/codetag.c~alloc_tag-allocate-percpu-counters-for-module-tags-dynamically +++ a/lib/codetag.c @@ -194,7 +194,7 @@ static int codetag_module_init(struct co if (err >= 0) { cttype->count += range_size(cttype, &range); if (cttype->desc.module_load) - cttype->desc.module_load(cttype, cmod); + cttype->desc.module_load(mod, range.start, range.stop); } up_write(&cttype->mod_lock);
@@ -333,7 +333,8 @@ void codetag_unload_module(struct module } if (found) { if (cttype->desc.module_unload) - cttype->desc.module_unload(cttype, cmod); + cttype->desc.module_unload(cmod->mod, + cmod->range.start, cmod->range.stop);
cttype->count -= range_size(cttype, &cmod->range); idr_remove(&cttype->mod_idr, mod_id); _
Patches currently in -mm which might be from surenb@google.com are
alloc_tag-allocate-percpu-counters-for-module-tags-dynamically.patch