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uprobes: Teach uprobe_copy_process() to handle CLONE_VFORK

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uprobe_copy_process() does nothing if the child shares ->mm with
the forking process, but there is a special case: CLONE_VFORK.
In this case it would be more correct to do dup_utask() but avoid
dup_xol(). This is not that important, the child should not unwind
its stack too much, this can corrupt the parent's stack, but at
least we need this to allow to ret-probe __vfork() itself.

Note: in theory, it would be better to check task_pt_regs(p)->sp
instead of CLONE_VFORK, we need to dup_utask() if and only if the
child can return from the function called by the parent. But this
needs the arch-dependant helper, and I think that nobody actually
does clone(same_stack, CLONE_VM).

Reported-by: Martin Cermak <mcermak@redhat.com>
Reported-by: David Smith <dsmith@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
This commit is contained in:
Oleg Nesterov 2013-10-16 19:39:37 +02:00
parent aa59c53fd4
commit 3ab6796617
3 changed files with 11 additions and 5 deletions
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4
include/linux/uprobes.h
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@ -117,7 +117,7 @@ extern void uprobe_start_dup_mmap(void);
extern void uprobe_end_dup_mmap(void); extern void uprobe_end_dup_mmap(void);
extern void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm); extern void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm);
extern void uprobe_free_utask(struct task_struct *t); extern void uprobe_free_utask(struct task_struct *t);
extern void uprobe_copy_process(struct task_struct *t); extern void uprobe_copy_process(struct task_struct *t, unsigned long flags);
extern unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs); extern unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs);
extern int uprobe_post_sstep_notifier(struct pt_regs *regs); extern int uprobe_post_sstep_notifier(struct pt_regs *regs);
extern int uprobe_pre_sstep_notifier(struct pt_regs *regs); extern int uprobe_pre_sstep_notifier(struct pt_regs *regs);
@ -174,7 +174,7 @@ static inline unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
static inline void uprobe_free_utask(struct task_struct *t) static inline void uprobe_free_utask(struct task_struct *t)
{ {
} }
static inline void uprobe_copy_process(struct task_struct *t) static inline void uprobe_copy_process(struct task_struct *t, unsigned long flags)
{ {
} }
static inline void uprobe_clear_state(struct mm_struct *mm) static inline void uprobe_clear_state(struct mm_struct *mm)

10
kernel/events/uprobes.c
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@ -1415,7 +1415,7 @@ static void dup_xol_work(struct callback_head *work)
/* /*
* Called in context of a new clone/fork from copy_process. * Called in context of a new clone/fork from copy_process.
*/ */
void uprobe_copy_process(struct task_struct *t) void uprobe_copy_process(struct task_struct *t, unsigned long flags)
{ {
struct uprobe_task *utask = current->utask; struct uprobe_task *utask = current->utask;
struct mm_struct *mm = current->mm; struct mm_struct *mm = current->mm;
@ -1424,7 +1424,10 @@ void uprobe_copy_process(struct task_struct *t)
t->utask = NULL; t->utask = NULL;
if (mm == t->mm || !utask || !utask->return_instances) if (!utask || !utask->return_instances)
return;
if (mm == t->mm && !(flags & CLONE_VFORK))
return; return;
if (dup_utask(t, utask)) if (dup_utask(t, utask))
@ -1435,6 +1438,9 @@ void uprobe_copy_process(struct task_struct *t)
if (!area) if (!area)
return uprobe_warn(t, "dup xol area"); return uprobe_warn(t, "dup xol area");
if (mm == t->mm)
return;
/* TODO: move it into the union in uprobe_task */ /* TODO: move it into the union in uprobe_task */
work = kmalloc(sizeof(*work), GFP_KERNEL); work = kmalloc(sizeof(*work), GFP_KERNEL);
if (!work) if (!work)

2
kernel/fork.c
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@ -1489,7 +1489,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
perf_event_fork(p); perf_event_fork(p);
trace_task_newtask(p, clone_flags); trace_task_newtask(p, clone_flags);
uprobe_copy_process(p); uprobe_copy_process(p, clone_flags);
return p; return p;