mm/alloc_tag: fix the kmemleak false positive issue in the allocation of the percpu variable tag->counters

When loading a module, as long as the module has memory allocation operations, kmemleak produces a false positive report that resembles the following: unreferenced object (percpu) 0x7dfd232a1650 (size 16): comm "modprobe", pid 1301, jiffies 4294940249 hex dump (first 16 bytes on cpu 2): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace (crc 0): kmemleak_alloc_percpu+0xb4/0xd0 pcpu_alloc_noprof+0x700/0x1098 load_module+0xd4/0x348 codetag_module_init+0x20c/0x450 codetag_load_module+0x70/0xb8 load_module+0xef8/0x1608 init_module_from_file+0xec/0x158 idempotent_init_module+0x354/0x608 __arm64_sys_finit_module+0xbc/0x150 invoke_syscall+0xd4/0x258 el0_svc_common.constprop.0+0xb4/0x240 do_el0_svc+0x48/0x68 el0_svc+0x40/0xf8 el0t_64_sync_handler+0x10c/0x138 el0t_64_sync+0x1ac/0x1b0 This is because the module can only indirectly reference alloc_tag_counters through the alloc_tag section, which misleads kmemleak. However, we don't have a kmemleak ignore interface for percpu allocations yet. So let's create one and invoke it for tag->counters. [gehao@kylinos.cn: fix build error when CONFIG_DEBUG_KMEMLEAK=n, s/igonore/ignore/] Link: https://lkml.kernel.org/r/20250620093102.2416767-1-hao.ge@linux.dev Link: https://lkml.kernel.org/r/20250619183154.2122608-1-hao.ge@linux.dev Fixes: 12ca42c23775 ("alloc_tag: allocate percpu counters for module tags dynamically") Signed-off-by: Hao Ge <gehao@kylinos.cn> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Suren Baghdasaryan <surenb@google.com> [lib/alloc_tag.c] Cc: Kent Overstreet <kent.overstreet@linux.dev> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Hao Ge committed 1 year ago

Commit f5769351 parent df831e93 files · +25 −1Browse files

Unified · Split

3 files

include/linux/kmemleak.h +4 −0
lib/alloc_tag.c +7 −1
mm/kmemleak.c +14 −0

include/linux/kmemleak.h+4−0

@@ -28,6 +28,7 @@ extern void kmemleak_update_trace(const void *ptr) __ref; · 27 unmodified lines
28	28	extern void kmemleak_not_leak(const void *ptr) __ref;
29	29	extern void kmemleak_transient_leak(const void *ptr) __ref;
30	30	extern void kmemleak_ignore(const void *ptr) __ref;
	31	+extern void kmemleak_ignore_percpu(const void __percpu *ptr) __ref;
31	32	extern void kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp) __ref;
32	33	extern void kmemleak_no_scan(const void *ptr) __ref;
33	34	extern void kmemleak_alloc_phys(phys_addr_t phys, size_t size,
@@ -97,6 +98,9 @@ static inline void kmemleak_not_leak(const void *ptr) · 63 unmodified lines
97	98	static inline void kmemleak_transient_leak(const void *ptr)
98	99	{
99	100	}
	101	+static inline void kmemleak_ignore_percpu(const void __percpu *ptr)
	102	+{
	103	+}
100	104	static inline void kmemleak_ignore(const void *ptr)
101	105	{
102	106	}

lib/alloc_tag.c+7−1

@@ -10,6 +10,7 @@ · 9 unmodified lines
10	10	#include <linux/seq_buf.h>
11	11	#include <linux/seq_file.h>
12	12	#include <linux/vmalloc.h>
	13	+#include <linux/kmemleak.h>
13	14
14	15	#define ALLOCINFO_FILE_NAME "allocinfo"
15	16	#define MODULE_ALLOC_TAG_VMAP_SIZE (100000UL * sizeof(struct alloc_tag))
@@ -632,8 +633,13 @@ static int load_module(struct module mod, struct codetag start, struct codetag · 616 unmodified lines
632	633	mod->name);
633	634	return -ENOMEM;
634	635	}
635		− }
636	636
	637	+ /*
	638	+ * Avoid a kmemleak false positive. The pointer to the counters is stored
	639	+ * in the alloc_tag section of the module and cannot be directly accessed.
	640	+ */
	641	+ kmemleak_ignore_percpu(tag->counters);
	642	+ }
637	643	return 0;
638	644	}
639	645

mm/kmemleak.c+14−0

@@ -1246,6 +1246,20 @@ void __ref kmemleak_transient_leak(const void *ptr) · 1245 unmodified lines
1246	1246	}
1247	1247	EXPORT_SYMBOL(kmemleak_transient_leak);
1248	1248
	1249	+/**
	1250	+ * kmemleak_ignore_percpu - similar to kmemleak_ignore but taking a percpu
	1251	+ * address argument
	1252	+ * @ptr: percpu address of the object
	1253	+ */
	1254	+void __ref kmemleak_ignore_percpu(const void __percpu *ptr)
	1255	+{
	1256	+ pr_debug("%s(0x%px)\n", __func__, ptr);
	1257	+
	1258	+ if (kmemleak_enabled && ptr && !IS_ERR_PCPU(ptr))
	1259	+ make_black_object((unsigned long)ptr, OBJECT_PERCPU);
	1260	+}
	1261	+EXPORT_SYMBOL_GPL(kmemleak_ignore_percpu);
	1262	+
1249	1263	/**
1250	1264	* kmemleak_ignore - ignore an allocated object
1251	1265	* @ptr: pointer to beginning of the object