2020-01-20 23:30:55

by Al Viro

Subject: [PATCH][bpf] don't bother with getname/kern_path - use user_path_at

kernel/bpf/inode.c misuses kern_path...() - it's much simpler
(and more efficient, on top of that) to use user_path...() counterparts
rather than bothering with doing getname() manually.

Signed-off-by: Al Viro <[email protected]>
---
diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index ecf42bec38c0..e11059b99f18 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -380,7 +380,7 @@ static const struct inode_operations bpf_dir_iops = {
.unlink = simple_unlink,
};

-static int bpf_obj_do_pin(const struct filename *pathname, void *raw,
+static int bpf_obj_do_pin(const char __user *pathname, void *raw,
enum bpf_type type)
{
struct dentry *dentry;
@@ -389,7 +389,7 @@ static int bpf_obj_do_pin(const struct filename *pathname, void *raw,
umode_t mode;
int ret;

- dentry = kern_path_create(AT_FDCWD, pathname->name, &path, 0);
+ dentry = user_path_create(AT_FDCWD, pathname, &path, 0);
if (IS_ERR(dentry))
return PTR_ERR(dentry);

@@ -422,30 +422,22 @@ static int bpf_obj_do_pin(const struct filename *pathname, void *raw,

int bpf_obj_pin_user(u32 ufd, const char __user *pathname)
{
- struct filename *pname;
enum bpf_type type;
void *raw;
int ret;

- pname = getname(pathname);
- if (IS_ERR(pname))
- return PTR_ERR(pname);
-
raw = bpf_fd_probe_obj(ufd, &type);
- if (IS_ERR(raw)) {
- ret = PTR_ERR(raw);
- goto out;
- }
+ if (IS_ERR(raw))
+ return PTR_ERR(raw);

- ret = bpf_obj_do_pin(pname, raw, type);
+ ret = bpf_obj_do_pin(pathname, raw, type);
if (ret != 0)
bpf_any_put(raw, type);
-out:
- putname(pname);
+
return ret;
}

-static void *bpf_obj_do_get(const struct filename *pathname,
+static void *bpf_obj_do_get(const char __user *pathname,
enum bpf_type *type, int flags)
{
struct inode *inode;
@@ -453,7 +445,7 @@ static void *bpf_obj_do_get(const struct filename *pathname,
void *raw;
int ret;

- ret = kern_path(pathname->name, LOOKUP_FOLLOW, &path);
+ ret = user_path_at(AT_FDCWD, pathname, LOOKUP_FOLLOW, &path);
if (ret)
return ERR_PTR(ret);

@@ -480,36 +472,27 @@ static void *bpf_obj_do_get(const struct filename *pathname,
int bpf_obj_get_user(const char __user *pathname, int flags)
{
enum bpf_type type = BPF_TYPE_UNSPEC;
- struct filename *pname;
- int ret = -ENOENT;
int f_flags;
void *raw;
+ int ret;

f_flags = bpf_get_file_flag(flags);
if (f_flags < 0)
return f_flags;

- pname = getname(pathname);
- if (IS_ERR(pname))
- return PTR_ERR(pname);
-
- raw = bpf_obj_do_get(pname, &type, f_flags);
- if (IS_ERR(raw)) {
- ret = PTR_ERR(raw);
- goto out;
- }
+ raw = bpf_obj_do_get(pathname, &type, f_flags);
+ if (IS_ERR(raw))
+ return PTR_ERR(raw);

if (type == BPF_TYPE_PROG)
ret = bpf_prog_new_fd(raw);
else if (type == BPF_TYPE_MAP)
ret = bpf_map_new_fd(raw, f_flags);
else
- goto out;
+ return -ENOENT;

if (ret < 0)
bpf_any_put(raw, type);
-out:
- putname(pname);
return ret;
}

2020-01-21 23:35:07

by Daniel Borkmann

Subject: Re: [PATCH][bpf] don't bother with getname/kern_path - use user_path_at

On 1/21/20 12:28 AM, Al Viro wrote:
> kernel/bpf/inode.c misuses kern_path...() - it's much simpler
> (and more efficient, on top of that) to use user_path...() counterparts
> rather than bothering with doing getname() manually.
>
> Signed-off-by: Al Viro <[email protected]>

Looks good, applied, thanks!