[PATCHv4 04/13] uprobes/x86: Unmap trampoline vma object in case it's unused

[Jiri Olsa <jolsa@kernel.org>]

In case the optimization fails, we leak new-ly created trampoline
vma mapping (in case we just created it), let's unmap it.

Fixes: ba2bfc97b462 ("uprobes/x86: Add support to optimize uprobes")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 arch/x86/kernel/uprobes.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index c8af41ed681a..af5af7d67999 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -677,11 +677,14 @@ static unsigned long find_nearest_trampoline(unsigned long vaddr)
 	return high_tramp;
 }
 
-static struct vm_area_struct *get_uprobe_trampoline(struct mm_struct *mm, unsigned long vaddr)
+static struct vm_area_struct *get_uprobe_trampoline(struct mm_struct *mm, unsigned long vaddr,
+						    bool *new_mapping)
 {
 	VMA_ITERATOR(vmi, mm, 0);
 	struct vm_area_struct *vma;
 
+	*new_mapping = false;
+
 	if (vaddr > TASK_SIZE || vaddr < PAGE_SIZE)
 		return ERR_PTR(-EINVAL);
 
@@ -696,6 +699,7 @@ static struct vm_area_struct *get_uprobe_trampoline(struct mm_struct *mm, unsign
 	if (IS_ERR_VALUE(vaddr))
 		return ERR_PTR(vaddr);
 
+	*new_mapping = true;
 	return _install_special_mapping(mm, vaddr, PAGE_SIZE,
 				VM_READ|VM_EXEC|VM_MAYEXEC|VM_MAYREAD|VM_IO,
 				&tramp_mapping);
@@ -1053,16 +1057,21 @@ static int __arch_uprobe_optimize(struct arch_uprobe *auprobe, struct mm_struct
 {
 	struct pt_regs *regs = task_pt_regs(current);
 	struct vm_area_struct *vma, *tramp;
+	bool new_mapping;
+	int ret;
 
 	if (!user_64bit_mode(regs))
 		return -EINVAL;
 	vma = find_vma(mm, vaddr);
 	if (!vma)
 		return -EINVAL;
-	tramp = get_uprobe_trampoline(mm, vaddr);
+	tramp = get_uprobe_trampoline(mm, vaddr, &new_mapping);
 	if (IS_ERR(tramp))
 		return PTR_ERR(tramp);
-	return WARN_ON_ONCE(swbp_optimize(auprobe, vma, vaddr, tramp->vm_start));
+	ret = swbp_optimize(auprobe, vma, vaddr, tramp->vm_start);
+	if (WARN_ON_ONCE(ret) && new_mapping)
+		WARN_ON_ONCE(do_munmap(mm, tramp->vm_start, PAGE_SIZE, NULL));
+	return ret;
 }
 
 void arch_uprobe_optimize(struct arch_uprobe *auprobe, unsigned long vaddr)
-- 
2.54.0