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Commit 2c42cfbf authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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perf: Change zero-padding of strings in perf_event_mmap_event() 



Oleg complained about the excessive 0-ing in perf_event_mmap_event(),
so try and be smarter about it while keeping it fairly fool proof and
avoid leaking random bits out to userspace.

Suggested-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-8jirlm99m6if2z13wd6rbyu6@git.kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 3ea2f2b9

kernel/events/core.c

+11 −6
Original line number Diff line number Diff line
@@ -5106,15 +5106,13 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event) 
	unsigned int size;

	char tmp[16];

	char *buf = NULL;

	const char *name;



	memset(tmp, 0, sizeof(tmp));

	char *name;



	if (file) {

		struct inode *inode;

		dev_t dev;



		buf = kzalloc(PATH_MAX, GFP_KERNEL);

		buf = kmalloc(PATH_MAX, GFP_KERNEL);

		if (!buf) {

			name = strncpy(tmp, "//enomem", sizeof(tmp));

			goto got_name;
@@ -5137,7 +5135,7 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event) 
		min = MINOR(dev);



	} else {

		name = arch_vma_name(vma);

		name = (char *)arch_vma_name(vma);

		if (name) {

			name = strncpy(tmp, name, sizeof(tmp) - 1);

			tmp[sizeof(tmp) - 1] = '\0';
@@ -5160,7 +5158,14 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event) 
	}



got_name:

	size = ALIGN(strlen(name)+1, sizeof(u64));

	/*

	 * Since our buffer works in 8 byte units we need to align our string

	 * size to a multiple of 8. However, we must guarantee the tail end is

	 * zero'd out to avoid leaking random bits to userspace.

	 */

	size = strlen(name)+1;

	while (!IS_ALIGNED(size, sizeof(u64)))

		name[size++] = '\0';



	mmap_event->file_name = name;

	mmap_event->file_size = size;