uprobes: Fix prepare_uprobe() race with itself (4710f05f) · Commits · 戴 / test

install_breakpoint() is called under mm->mmap_sem, this protects set_swbp() but not prepare_uprobe(). Two or more different tasks can call install_breakpoint()->prepare_uprobe() 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 <oleg@redhat.com> Acked-by:

Srikar Dronamraju <srikar@linux.vnet.ibm.com>

kernel/events/uprobes.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -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 prepare_uprobe(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 prepare_uprobe(struct uprobe uprobe, struct file file,
		uprobe->flags \|= UPROBE_COPY_INSN;

		out:
		mutex_unlock(&uprobe->copy_mutex);

		return ret;
		}

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