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: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-8jirlm99m6if2z13wd6rbyu6@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -5106,15 +5106,13 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
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unsigned int size;
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unsigned int size;
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char tmp[16];
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char tmp[16];
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char *buf = NULL;
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char *buf = NULL;
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const char *name;
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char *name;
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memset(tmp, 0, sizeof(tmp));
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if (file) {
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if (file) {
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struct inode *inode;
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struct inode *inode;
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dev_t dev;
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dev_t dev;
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buf = kzalloc(PATH_MAX, GFP_KERNEL);
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buf = kmalloc(PATH_MAX, GFP_KERNEL);
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if (!buf) {
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if (!buf) {
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name = strncpy(tmp, "//enomem", sizeof(tmp));
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name = strncpy(tmp, "//enomem", sizeof(tmp));
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goto got_name;
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goto got_name;
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@ -5137,7 +5135,7 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
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min = MINOR(dev);
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min = MINOR(dev);
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} else {
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} else {
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name = arch_vma_name(vma);
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name = (char *)arch_vma_name(vma);
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if (name) {
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if (name) {
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name = strncpy(tmp, name, sizeof(tmp) - 1);
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name = strncpy(tmp, name, sizeof(tmp) - 1);
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tmp[sizeof(tmp) - 1] = '\0';
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tmp[sizeof(tmp) - 1] = '\0';
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@ -5160,7 +5158,14 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
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}
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}
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got_name:
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got_name:
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size = ALIGN(strlen(name)+1, sizeof(u64));
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/*
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* Since our buffer works in 8 byte units we need to align our string
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* size to a multiple of 8. However, we must guarantee the tail end is
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* zero'd out to avoid leaking random bits to userspace.
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*/
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size = strlen(name)+1;
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while (!IS_ALIGNED(size, sizeof(u64)))
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name[size++] = '\0';
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mmap_event->file_name = name;
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mmap_event->file_name = name;
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mmap_event->file_size = size;
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mmap_event->file_size = size;
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