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

[Jiri Olsa]

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 <jo...@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