| Message ID | 20240214112046.09a322d6@gandalf.local.home (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 2394ac4145ea91b92271e675a09af2a9ea6840b7 |
| Headers | show |
| Series | [v2] tracing: Inform kmemleak of saved_cmdlines allocation | expand |
Steven Rostedt <rostedt@goodmis.org> writes: > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > 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/ > > 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> Applies cleanly to v6.8-rc4 and I don't see the leak anymore, thank you for fixing it so quickly! Tested-by: Kalle Valo <kvalo@kernel.org>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index aa54810e8b56..8198bfc54b58 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -39,6 +39,7 @@ #include <linux/ctype.h> #include <linux/init.h> #include <linux/panic_notifier.h> +#include <linux/kmemleak.h> #include <linux/poll.h> #include <linux/nmi.h> #include <linux/fs.h> @@ -2339,6 +2340,7 @@ static void free_saved_cmdlines_buffer(struct 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); } @@ -2358,6 +2360,7 @@ static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val) return NULL; s = page_address(page); + kmemleak_alloc(s, size, 1, GFP_KERNEL); memset(s, 0, sizeof(*s)); /* Round up to actual allocation */