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proc: change ->nlink under proc_subdir_lock

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Currently gluing PDE into global /proc tree is done under lock, but
changing ->nlink is not.  Additionally struct proc_dir_entry::nlink is
not atomic so updates can be lost.

Link: http://lkml.kernel.org/r/20190925202436.GA17388@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alexey Dobriyan 2019-12-04 16:49:59 -08:00 committed by Linus Torvalds
parent 3cde287bb4
commit e06689bf57
1 changed files with 15 additions and 16 deletions
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31
fs/proc/generic.c
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@ -138,8 +138,12 @@ static int proc_getattr(const struct path *path, struct kstat *stat,
{
struct inode *inode = d_inode(path->dentry);
struct proc_dir_entry *de = PDE(inode);
if (de && de->nlink)
set_nlink(inode, de->nlink);
if (de) {
nlink_t nlink = READ_ONCE(de->nlink);
if (nlink > 0) {
set_nlink(inode, nlink);
}
}
generic_fillattr(inode, stat);
return 0;
@ -362,6 +366,7 @@ struct proc_dir_entry *proc_register(struct proc_dir_entry *dir,
write_unlock(&proc_subdir_lock);
goto out_free_inum;
}
dir->nlink++;
write_unlock(&proc_subdir_lock);
return dp;
@ -472,10 +477,7 @@ struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode,
ent->data = data;
ent->proc_fops = &proc_dir_operations;
ent->proc_iops = &proc_dir_inode_operations;
parent->nlink++;
ent = proc_register(parent, ent);
if (!ent)
parent->nlink--;
}
return ent;
}
@ -505,10 +507,7 @@ struct proc_dir_entry *proc_create_mount_point(const char *name)
ent->data = NULL;
ent->proc_fops = NULL;
ent->proc_iops = NULL;
parent->nlink++;
ent = proc_register(parent, ent);
if (!ent)
parent->nlink--;
}
return ent;
}
@ -666,8 +665,12 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
len = strlen(fn);
de = pde_subdir_find(parent, fn, len);
if (de)
if (de) {
rb_erase(&de->subdir_node, &parent->subdir);
if (S_ISDIR(de->mode)) {
parent->nlink--;
}
}
write_unlock(&proc_subdir_lock);
if (!de) {
WARN(1, "name '%s'\n", name);
@ -676,9 +679,6 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
proc_entry_rundown(de);
if (S_ISDIR(de->mode))
parent->nlink--;
de->nlink = 0;
WARN(pde_subdir_first(de),
"%s: removing non-empty directory '%s/%s', leaking at least '%s'\n",
__func__, de->parent->name, de->name, pde_subdir_first(de)->name);
@ -714,13 +714,12 @@ int remove_proc_subtree(const char *name, struct proc_dir_entry *parent)
de = next;
continue;
}
write_unlock(&proc_subdir_lock);
proc_entry_rundown(de);
next = de->parent;
if (S_ISDIR(de->mode))
next->nlink--;
de->nlink = 0;
write_unlock(&proc_subdir_lock);
proc_entry_rundown(de);
if (de == root)
break;
pde_put(de);