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authorIngo Molnar <mingo@elte.hu>2008-11-18 15:23:08 +0100
committerIngo Molnar <mingo@elte.hu>2008-11-18 15:34:36 +0100
commit10db4ef7b9a65b86e4d047671a1886f4c101a859 (patch)
tree2d47105e6cf1e88c5a83def331c5d6302578e607
parent93ce99e849433ede4ce8b410b749dc0cad1100b2 (diff)
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x86, PEBS/DS: fix code flow in ds_request()
this compiler warning: arch/x86/kernel/ds.c: In function 'ds_request': arch/x86/kernel/ds.c:368: warning: 'context' may be used uninitialized in this function Shows that the code flow in ds_request() is buggy - it goes into the unlock+release-context path even when the context is not allocated yet. First allocate the context, then do the other checks. Also, take care with GFP allocations under the ds_lock spinlock. Cc: <stable@kernel.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--arch/x86/kernel/ds.c26
1 files changed, 21 insertions, 5 deletions
diff --git a/arch/x86/kernel/ds.c b/arch/x86/kernel/ds.c
index ac1d5b0..d1a1214 100644
--- a/arch/x86/kernel/ds.c
+++ b/arch/x86/kernel/ds.c
@@ -236,17 +236,33 @@ static inline struct ds_context *ds_alloc_context(struct task_struct *task)
struct ds_context *context = *p_context;
if (!context) {
+ spin_unlock(&ds_lock);
+
context = kzalloc(sizeof(*context), GFP_KERNEL);
- if (!context)
+ if (!context) {
+ spin_lock(&ds_lock);
return NULL;
+ }
context->ds = kzalloc(ds_cfg.sizeof_ds, GFP_KERNEL);
if (!context->ds) {
kfree(context);
+ spin_lock(&ds_lock);
return NULL;
}
+ spin_lock(&ds_lock);
+ /*
+ * Check for race - another CPU could have allocated
+ * it meanwhile:
+ */
+ if (*p_context) {
+ kfree(context->ds);
+ kfree(context);
+ return *p_context;
+ }
+
*p_context = context;
context->this = p_context;
@@ -384,15 +400,15 @@ static int ds_request(struct task_struct *task, void *base, size_t size,
spin_lock(&ds_lock);
- error = -EPERM;
- if (!check_tracer(task))
- goto out_unlock;
-
error = -ENOMEM;
context = ds_alloc_context(task);
if (!context)
goto out_unlock;
+ error = -EPERM;
+ if (!check_tracer(task))
+ goto out_unlock;
+
error = -EALREADY;
if (context->owner[qual] == current)
goto out_unlock;