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authorAnton Blanchard <anton@samba.org>2009-07-16 15:15:52 +0200
committerIngo Molnar <mingo@elte.hu>2009-07-18 11:21:29 +0200
commit413ee3b48ab582ffea33e7e140c7a2c5ea657e9a (patch)
tree3ecf161d9db15c95ba0a4d02aa18e243b796a04b
parent23cdb5d5171d591ec911aada682e09d53c14a810 (diff)
perf_counter: Make sure we dont leak kernel memory to userspace
There are a few places we are leaking tiny amounts of kernel memory to userspace. This happens when writing out strings because we always align the end to 64 bits. To avoid this we should always use an appropriately sized temporary buffer and ensure it is zeroed. Since d_path assembles the string from the end of the buffer backwards, we need to add 64 bits after the buffer to allow for alignment. We also need to copy arch_vma_name to the temporary buffer, because if we use it directly we may end up copying to userspace a number of bytes after the end of the string constant. Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <20090716104817.273972048@samba.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/perf_counter.c19
1 files changed, 15 insertions, 4 deletions
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index c6c38fb7766..f7a8ab9576e 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -2968,8 +2968,10 @@ static void perf_counter_comm_event(struct perf_comm_event *comm_event)
struct perf_cpu_context *cpuctx;
struct perf_counter_context *ctx;
unsigned int size;
- char *comm = comm_event->task->comm;
+ char comm[TASK_COMM_LEN];
+ memset(comm, 0, sizeof(comm));
+ strncpy(comm, comm_event->task->comm, sizeof(comm));
size = ALIGN(strlen(comm)+1, sizeof(u64));
comm_event->comm = comm;
@@ -3088,8 +3090,15 @@ static void perf_counter_mmap_event(struct perf_mmap_event *mmap_event)
char *buf = NULL;
const char *name;
+ memset(tmp, 0, sizeof(tmp));
+
if (file) {
- buf = kzalloc(PATH_MAX, GFP_KERNEL);
+ /*
+ * d_path works from the end of the buffer backwards, so we
+ * need to add enough zero bytes after the string to handle
+ * the 64bit alignment we do later.
+ */
+ buf = kzalloc(PATH_MAX + sizeof(u64), GFP_KERNEL);
if (!buf) {
name = strncpy(tmp, "//enomem", sizeof(tmp));
goto got_name;
@@ -3100,9 +3109,11 @@ static void perf_counter_mmap_event(struct perf_mmap_event *mmap_event)
goto got_name;
}
} else {
- name = arch_vma_name(mmap_event->vma);
- if (name)
+ if (arch_vma_name(mmap_event->vma)) {
+ name = strncpy(tmp, arch_vma_name(mmap_event->vma),
+ sizeof(tmp));
goto got_name;
+ }
if (!vma->vm_mm) {
name = strncpy(tmp, "[vdso]", sizeof(tmp));