Commit cd9e2bb8 authored by Konstantin Khlebnikov's avatar Konstantin Khlebnikov Committed by Linus Torvalds
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proc: use down_read_killable mmap_sem for /proc/pid/map_files 

Do not remain stuck forever if something goes wrong.  Using a killable
lock permits cleanup of stuck tasks and simplifies investigation.

It seems ->d_revalidate() could return any error (except ECHILD) to abort
validation and pass error as result of lookup sequence.

[akpm@linux-foundation.org: fix proc_map_files_lookup() return value, per Andrei]
Link: http://lkml.kernel.org/r/156007493995.3335.9595044802115356911.stgit@buzz


Signed-off-by: default avatarKonstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: default avatarRoman Gushchin <guro@fb.com>
Reviewed-by: default avatarCyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c4603801

fs/proc/base.c

+22 −6
Original line number Diff line number Diff line
@@ -1962,10 +1962,13 @@ static int map_files_d_revalidate(struct dentry *dentry, unsigned int flags) 
		goto out;



	if (!dname_to_vma_addr(dentry, &vm_start, &vm_end)) {

		down_read(&mm->mmap_sem);

		exact_vma_exists = !!find_exact_vma(mm, vm_start, vm_end);

		status = down_read_killable(&mm->mmap_sem);

		if (!status) {

			exact_vma_exists = !!find_exact_vma(mm, vm_start,

							    vm_end);

			up_read(&mm->mmap_sem);

		}

	}



	mmput(mm);
@@ -2010,8 +2013,11 @@ static int map_files_get_link(struct dentry *dentry, struct path *path) 
	if (rc)

		goto out_mmput;



	rc = down_read_killable(&mm->mmap_sem);

	if (rc)

		goto out_mmput;



	rc = -ENOENT;

	down_read(&mm->mmap_sem);

	vma = find_exact_vma(mm, vm_start, vm_end);

	if (vma && vma->vm_file) {

		*path = vma->vm_file->f_path;
@@ -2107,7 +2113,11 @@ static struct dentry *proc_map_files_lookup(struct inode *dir, 
	if (!mm)

		goto out_put_task;



	down_read(&mm->mmap_sem);

	result = ERR_PTR(-EINTR);

	if (down_read_killable(&mm->mmap_sem))

		goto out_put_mm;



	result = ERR_PTR(-ENOENT);

	vma = find_exact_vma(mm, vm_start, vm_end);

	if (!vma)

		goto out_no_vma;
@@ -2118,6 +2128,7 @@ static struct dentry *proc_map_files_lookup(struct inode *dir, 


out_no_vma:

	up_read(&mm->mmap_sem);

out_put_mm:

	mmput(mm);

out_put_task:

	put_task_struct(task);
@@ -2160,7 +2171,12 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx) 
	mm = get_task_mm(task);

	if (!mm)

		goto out_put_task;

	down_read(&mm->mmap_sem);



	ret = down_read_killable(&mm->mmap_sem);

	if (ret) {

		mmput(mm);

		goto out_put_task;

	}



	nr_files = 0;