@@ -68,6 +68,8 @@ DEFINE_STATIC_SRCU(vmcore_cb_srcu);
static LIST_HEAD(vmcore_cb_list);
/* Whether the vmcore has been opened once. */
static bool vmcore_opened;
+/* Whether the vmcore is currently open. */
+static unsigned int vmcore_open;
void register_vmcore_cb(struct vmcore_cb *cb)
{
@@ -122,6 +124,20 @@ static int open_vmcore(struct inode *inode, struct file *file)
{
mutex_lock(&vmcore_mutex);
vmcore_opened = true;
+ if (vmcore_open + 1 == 0) {
+ mutex_unlock(&vmcore_mutex);
+ return -EBUSY;
+ }
+ vmcore_open++;
+ mutex_unlock(&vmcore_mutex);
+
+ return 0;
+}
+
+static int release_vmcore(struct inode *inode, struct file *file)
+{
+ mutex_lock(&vmcore_mutex);
+ vmcore_open--;
mutex_unlock(&vmcore_mutex);
return 0;
@@ -243,33 +259,27 @@ static int vmcoredd_copy_dumps(struct iov_iter *iter, u64 start, size_t size)
{
struct vmcoredd_node *dump;
u64 offset = 0;
- int ret = 0;
size_t tsz;
char *buf;
- mutex_lock(&vmcore_mutex);
list_for_each_entry(dump, &vmcoredd_list, list) {
if (start < offset + dump->size) {
tsz = min(offset + (u64)dump->size - start, (u64)size);
buf = dump->buf + start - offset;
- if (copy_to_iter(buf, tsz, iter) < tsz) {
- ret = -EFAULT;
- goto out_unlock;
- }
+ if (copy_to_iter(buf, tsz, iter) < tsz)
+ return -EFAULT;
size -= tsz;
start += tsz;
/* Leave now if buffer filled already */
if (!size)
- goto out_unlock;
+ return 0;
}
offset += dump->size;
}
-out_unlock:
- mutex_unlock(&vmcore_mutex);
- return ret;
+ return 0;
}
#ifdef CONFIG_MMU
@@ -278,20 +288,16 @@ static int vmcoredd_mmap_dumps(struct vm_area_struct *vma, unsigned long dst,
{
struct vmcoredd_node *dump;
u64 offset = 0;
- int ret = 0;
size_t tsz;
char *buf;
- mutex_lock(&vmcore_mutex);
list_for_each_entry(dump, &vmcoredd_list, list) {
if (start < offset + dump->size) {
tsz = min(offset + (u64)dump->size - start, (u64)size);
buf = dump->buf + start - offset;
if (remap_vmalloc_range_partial(vma, dst, buf, 0,
- tsz)) {
- ret = -EFAULT;
- goto out_unlock;
- }
+ tsz))
+ return -EFAULT;
size -= tsz;
start += tsz;
@@ -299,14 +305,12 @@ static int vmcoredd_mmap_dumps(struct vm_area_struct *vma, unsigned long dst,
/* Leave now if buffer filled already */
if (!size)
- goto out_unlock;
+ return 0;
}
offset += dump->size;
}
-out_unlock:
- mutex_unlock(&vmcore_mutex);
- return ret;
+ return 0;
}
#endif /* CONFIG_MMU */
#endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */
@@ -691,6 +695,7 @@ static int mmap_vmcore(struct file *file, struct vm_area_struct *vma)
static const struct proc_ops vmcore_proc_ops = {
.proc_open = open_vmcore,
+ .proc_release = release_vmcore,
.proc_read_iter = read_vmcore,
.proc_lseek = default_llseek,
.proc_mmap = mmap_vmcore,
@@ -1516,12 +1521,18 @@ int vmcore_add_device_dump(struct vmcoredd_data *data)
dump->buf = buf;
dump->size = data_size;
- /* Add the dump to driver sysfs list */
+ /* Add the dump to driver sysfs list and update the elfcore hdr */
mutex_lock(&vmcore_mutex);
- list_add_tail(&dump->list, &vmcoredd_list);
- mutex_unlock(&vmcore_mutex);
+ if (vmcore_opened)
+ pr_warn_once("Unexpected adding of device dump\n");
+ if (vmcore_open) {
+ ret = -EBUSY;
+ goto out_err;
+ }
+ list_add_tail(&dump->list, &vmcoredd_list);
vmcoredd_update_size(data_size);
+ mutex_unlock(&vmcore_mutex);
return 0;
out_err:
The vmcoredd_update_size() call and its effects (size/offset changes) are currently completely unsynchronized, and will cause trouble when performed concurrently, or when done while someone is already reading the vmcore. Let's protect all vmcore modifications by the vmcore_mutex, disallow vmcore modifications while the vmcore is open, and warn on vmcore modifications after the vmcore was already opened once: modifications while the vmcore is open are unsafe, and modifications after the vmcore was opened indicates trouble. Properly synchronize against concurrent opening of the vmcore. No need to grab the mutex during mmap()/read(): after we opened the vmcore, modifications are impossible. It's worth noting that modifications after the vmcore was opened are completely unexpected, so failing if open, and warning if already opened (+closed again) is good enough. This change not only handles concurrent adding of device dumps + concurrent reading of the vmcore properly, it also prepares for other mechanisms that will modify the vmcore. Signed-off-by: David Hildenbrand <david@redhat.com> --- fs/proc/vmcore.c | 57 +++++++++++++++++++++++++++++------------------- 1 file changed, 34 insertions(+), 23 deletions(-)