[PATCH 1/2] mm_for_maps: shift down_read(mmap_sem) to the caller
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[PATCH 1/2] mm_for_maps: shift down_read(mmap_sem) to the caller
by Oleg Nesterov-3
::
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mm_for_maps() takes ->mmap_sem after security checks, this looks
strange and obfuscates the locking rules. Move this lock to its single caller, m_start(). Signed-off-by: Oleg Nesterov <oleg@...> --- fs/proc/task_mmu.c | 1 + fs/proc/task_nommu.c | 1 + fs/proc/base.c | 8 +++----- 3 files changed, 5 insertions(+), 5 deletions(-) --- WAIT/fs/proc/task_mmu.c~1_MOVE_MMAP_SEM 2009-05-03 17:15:27.000000000 +0200 +++ WAIT/fs/proc/task_mmu.c 2009-07-10 02:00:56.000000000 +0200 @@ -119,6 +119,7 @@ static void *m_start(struct seq_file *m, mm = mm_for_maps(priv->task); if (!mm) return NULL; + down_read(&mm->mmap_sem); tail_vma = get_gate_vma(priv->task); priv->tail_vma = tail_vma; --- WAIT/fs/proc/task_nommu.c~1_MOVE_MMAP_SEM 2009-04-09 00:39:09.000000000 +0200 +++ WAIT/fs/proc/task_nommu.c 2009-07-10 02:01:25.000000000 +0200 @@ -189,6 +189,7 @@ static void *m_start(struct seq_file *m, priv->task = NULL; return NULL; } + down_read(&mm->mmap_sem); /* start from the Nth VMA */ for (p = rb_first(&mm->mm_rb); p; p = rb_next(p)) --- WAIT/fs/proc/base.c~1_MOVE_MMAP_SEM 2009-07-09 17:56:27.000000000 +0200 +++ WAIT/fs/proc/base.c 2009-07-10 02:05:14.000000000 +0200 @@ -235,9 +235,8 @@ static int check_mem_permission(struct t struct mm_struct *mm_for_maps(struct task_struct *task) { struct mm_struct *mm = get_task_mm(task); - if (!mm) - return NULL; - if (mm != current->mm) { + + if (mm && mm != current->mm) { /* * task->mm can be changed before security check, * in that case we must notice the change after. @@ -245,10 +244,9 @@ struct mm_struct *mm_for_maps(struct tas if (!ptrace_may_access(task, PTRACE_MODE_READ) || mm != task->mm) { mmput(mm); - return NULL; + mm = NULL; } } - down_read(&mm->mmap_sem); return mm; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@... More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |
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Re: [PATCH 1/2] mm_for_maps: shift down_read(mmap_sem) to the caller
by Serge E. Hallyn
::
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Quoting Oleg Nesterov (oleg@...):
> mm_for_maps() takes ->mmap_sem after security checks, this looks > strange and obfuscates the locking rules. Move this lock to its > single caller, m_start(). > > Signed-off-by: Oleg Nesterov <oleg@...> Looks sane. Acked-by: Serge Hallyn <serue@...> > --- > > fs/proc/task_mmu.c | 1 + > fs/proc/task_nommu.c | 1 + > fs/proc/base.c | 8 +++----- > 3 files changed, 5 insertions(+), 5 deletions(-) > > --- WAIT/fs/proc/task_mmu.c~1_MOVE_MMAP_SEM 2009-05-03 17:15:27.000000000 +0200 > +++ WAIT/fs/proc/task_mmu.c 2009-07-10 02:00:56.000000000 +0200 > @@ -119,6 +119,7 @@ static void *m_start(struct seq_file *m, > mm = mm_for_maps(priv->task); > if (!mm) > return NULL; > + down_read(&mm->mmap_sem); > > tail_vma = get_gate_vma(priv->task); > priv->tail_vma = tail_vma; > --- WAIT/fs/proc/task_nommu.c~1_MOVE_MMAP_SEM 2009-04-09 00:39:09.000000000 +0200 > +++ WAIT/fs/proc/task_nommu.c 2009-07-10 02:01:25.000000000 +0200 > @@ -189,6 +189,7 @@ static void *m_start(struct seq_file *m, > priv->task = NULL; > return NULL; > } > + down_read(&mm->mmap_sem); > > /* start from the Nth VMA */ > for (p = rb_first(&mm->mm_rb); p; p = rb_next(p)) > --- WAIT/fs/proc/base.c~1_MOVE_MMAP_SEM 2009-07-09 17:56:27.000000000 +0200 > +++ WAIT/fs/proc/base.c 2009-07-10 02:05:14.000000000 +0200 > @@ -235,9 +235,8 @@ static int check_mem_permission(struct t > struct mm_struct *mm_for_maps(struct task_struct *task) > { > struct mm_struct *mm = get_task_mm(task); > - if (!mm) > - return NULL; > - if (mm != current->mm) { > + > + if (mm && mm != current->mm) { > /* > * task->mm can be changed before security check, > * in that case we must notice the change after. > @@ -245,10 +244,9 @@ struct mm_struct *mm_for_maps(struct tas > if (!ptrace_may_access(task, PTRACE_MODE_READ) || > mm != task->mm) { > mmput(mm); > - return NULL; > + mm = NULL; > } > } > - down_read(&mm->mmap_sem); > return mm; > } > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@... More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |
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