Commit 2c42cfbf authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar

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