5.4-stable review patch. If anyone has any objections, please let me know.
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From: Steven Rostedt (Google) rostedt@goodmis.org
commit 2394ac4145ea91b92271e675a09af2a9ea6840b7 upstream.
The allocation of the struct saved_cmdlines_buffer structure changed from:
s = kmalloc(sizeof(*s), GFP_KERNEL); s->saved_cmdlines = kmalloc_array(TASK_COMM_LEN, val, GFP_KERNEL);
to:
orig_size = sizeof(*s) + val * TASK_COMM_LEN; order = get_order(orig_size); size = 1 << (order + PAGE_SHIFT); page = alloc_pages(GFP_KERNEL, order); if (!page) return NULL;
s = page_address(page); memset(s, 0, sizeof(*s));
s->saved_cmdlines = kmalloc_array(TASK_COMM_LEN, val, GFP_KERNEL);
Where that s->saved_cmdlines allocation looks to be a dangling allocation to kmemleak. That's because kmemleak only keeps track of kmalloc() allocations. For allocations that use page_alloc() directly, the kmemleak needs to be explicitly informed about it.
Add kmemleak_alloc() and kmemleak_free() around the page allocation so that it doesn't give the following false positive:
unreferenced object 0xffff8881010c8000 (size 32760): comm "swapper", pid 0, jiffies 4294667296 hex dump (first 32 bytes): ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................ ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................ backtrace (crc ae6ec1b9): [<ffffffff86722405>] kmemleak_alloc+0x45/0x80 [<ffffffff8414028d>] __kmalloc_large_node+0x10d/0x190 [<ffffffff84146ab1>] __kmalloc+0x3b1/0x4c0 [<ffffffff83ed7103>] allocate_cmdlines_buffer+0x113/0x230 [<ffffffff88649c34>] tracer_alloc_buffers.isra.0+0x124/0x460 [<ffffffff8864a174>] early_trace_init+0x14/0xa0 [<ffffffff885dd5ae>] start_kernel+0x12e/0x3c0 [<ffffffff885f5758>] x86_64_start_reservations+0x18/0x30 [<ffffffff885f582b>] x86_64_start_kernel+0x7b/0x80 [<ffffffff83a001c3>] secondary_startup_64_no_verify+0x15e/0x16b
Link: https://lore.kernel.org/linux-trace-kernel/87r0hfnr9r.fsf@kernel.org/ Link: https://lore.kernel.org/linux-trace-kernel/20240214112046.09a322d6@gandalf.l...
Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Catalin Marinas catalin.marinas@arm.com Fixes: 44dc5c41b5b1 ("tracing: Fix wasted memory in saved_cmdlines logic") Reported-by: Kalle Valo kvalo@kernel.org Tested-by: Kalle Valo kvalo@kernel.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/trace/trace.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -39,6 +39,7 @@ #include <linux/slab.h> #include <linux/ctype.h> #include <linux/init.h> +#include <linux/kmemleak.h> #include <linux/poll.h> #include <linux/nmi.h> #include <linux/fs.h> @@ -1996,6 +1997,7 @@ static void free_saved_cmdlines_buffer(s int order = get_order(sizeof(*s) + s->cmdline_num * TASK_COMM_LEN);
kfree(s->map_cmdline_to_pid); + kmemleak_free(s); free_pages((unsigned long)s, order); }
@@ -2015,6 +2017,7 @@ static struct saved_cmdlines_buffer *all return NULL;
s = page_address(page); + kmemleak_alloc(s, size, 1, GFP_KERNEL); memset(s, 0, sizeof(*s));
/* Round up to actual allocation */