install_breakpoint() is called under mm->mmap_sem, this protects
set_swbp() but not uprobe_copy_insn(). Two or more different tasks
can call install_breakpoint()->uprobe_copy_insn() at the same time,
this leads to numerous problems if UPROBE_COPY_INSN is not set.
Just for example, the second copy_insn() can corrupt the already
analyzed/fixuped uprobe->arch.insn and race with handle_swbp().
This patch simply adds uprobe->copy_mutex to serialize this code.
We could probably reuse ->consumer_rwsem, but this would mean that
consumer->handler() can not use mm->mmap_sem, not good.
Note: this is another temporary ugly hack until we move this logic
into uprobe_register().
Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
kernel/events/uprobes.c | 8 ++++++++
1 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 5c0c1b0..8410388 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -89,6 +89,7 @@ struct uprobe {
struct rb_node rb_node; /* node in the rb tree */
atomic_t ref;
struct rw_semaphore consumer_rwsem;
+ struct mutex copy_mutex; /* TODO: kill me and
UPROBE_COPY_INSN */
struct list_head pending_list;
struct uprobe_consumer *consumers;
struct inode *inode; /* Also hold a ref to inode */
@@ -444,6 +445,7 @@ static struct uprobe *alloc_uprobe(struct inode *inode,
loff_t offset)
uprobe->inode = igrab(inode);
uprobe->offset = offset;
init_rwsem(&uprobe->consumer_rwsem);
+ mutex_init(&uprobe->copy_mutex);
/* add to uprobes_tree, sorted on inode:offset */
cur_uprobe = insert_uprobe(uprobe);
@@ -578,6 +580,10 @@ static int uprobe_copy_insn(struct uprobe *uprobe, struct
file *file,
if (uprobe->flags & UPROBE_COPY_INSN)
return ret;
+ mutex_lock(&uprobe->copy_mutex);
+ if (uprobe->flags & UPROBE_COPY_INSN)
+ goto out;
+
ret = copy_insn(uprobe, file);
if (ret)
goto out;
@@ -598,6 +604,8 @@ static int uprobe_copy_insn(struct uprobe *uprobe, struct
file *file,
uprobe->flags |= UPROBE_COPY_INSN;
ret = 0;
out:
+ mutex_unlock(&uprobe->copy_mutex);
+
return ret;
}
--
1.5.5.1
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