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proc: use down_read_killable mmap_sem for /proc/pid/map_files

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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: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Michal 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Konstantin Khlebnikov 2019-07-11 21:00:03 -07:00 committed by Linus Torvalds
parent c46038017f
commit cd9e2bb827
1 changed files with 22 additions and 6 deletions
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28
fs/proc/base.c
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@ -1962,9 +1962,12 @@ 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);
up_read(&mm->mmap_sem);
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;