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authorPeter Zijlstra <peterz@infradead.org>2013-10-17 00:06:46 +0200
committerIngo Molnar <mingo@kernel.org>2013-10-29 12:02:53 +0100
commit2c42cfbfe10872929c2ba1f8130e31063ff59b94 (patch)
tree588f6008befc05e2458ab0bfc8bde08315279333 /kernel/events
parent3ea2f2b96f9e636f49eb10962e96db3e19cab157 (diff)
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>
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/core.c17
1 files changed, 11 insertions, 6 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index b409e757cadc..85a8bbde6481 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -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;