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Subject[PATCH 08/24] fs: add a kern_access helper
Date
Add a simple helper for a access with a kernelspace name and use it in
the early init code instead of relying on the implicit set_fs(KERNEL_DS)
there. Remove the now unused ksys_access.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/open.c | 37 +++++++++++++++++++++++++------------
include/linux/fs.h | 1 +
include/linux/syscalls.h | 7 -------
init/main.c | 3 +--
4 files changed, 27 insertions(+), 21 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index 424db905da5f18..2a9457a16b2be2 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -394,19 +394,19 @@ static const struct cred *access_override_creds(void)
return old_cred;
}

-long do_faccessat(int dfd, const char __user *filename, int mode, int flags)
+static int do_faccessat(int dfd, struct filename *name, int mode, int flags)
{
struct path path;
struct inode *inode;
- int res;
+ int res = -EINVAL;
unsigned int lookup_flags = LOOKUP_FOLLOW;
const struct cred *old_cred = NULL;

if (mode & ~S_IRWXO) /* where's F_OK, X_OK, W_OK, R_OK? */
- return -EINVAL;
+ goto out_putname;

if (flags & ~(AT_EACCESS | AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH))
- return -EINVAL;
+ goto out_putname;

if (flags & AT_SYMLINK_NOFOLLOW)
lookup_flags &= ~LOOKUP_FOLLOW;
@@ -414,15 +414,16 @@ long do_faccessat(int dfd, const char __user *filename, int mode, int flags)
lookup_flags |= LOOKUP_EMPTY;

if (!(flags & AT_EACCESS)) {
+ res = -ENOMEM;
old_cred = access_override_creds();
if (!old_cred)
- return -ENOMEM;
+ goto out_putname;
}

retry:
- res = user_path_at(dfd, filename, lookup_flags, &path);
+ res = filename_lookup(dfd, name, lookup_flags, &path, NULL);
if (res)
- goto out;
+ goto out_revert_creds;

inode = d_backing_inode(path.dentry);

@@ -459,27 +460,39 @@ long do_faccessat(int dfd, const char __user *filename, int mode, int flags)
lookup_flags |= LOOKUP_REVAL;
goto retry;
}
-out:
+ putname(name);
+out_revert_creds:
if (old_cred)
revert_creds(old_cred);
-
return res;
+out_putname:
+ if (!IS_ERR(name))
+ putname(name);
+ return res;
+}
+
+int __init kern_access(const char __user *filename, int mode)
+{
+ return do_faccessat(AT_FDCWD, getname_kernel(filename), mode, 0);
}

SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
{
- return do_faccessat(dfd, filename, mode, 0);
+ return do_faccessat(dfd, getname(filename), mode, 0);
}

SYSCALL_DEFINE4(faccessat2, int, dfd, const char __user *, filename, int, mode,
int, flags)
{
- return do_faccessat(dfd, filename, mode, flags);
+ unsigned int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
+ struct filename *name = getname_flags(filename, lookup_flags, NULL);
+
+ return do_faccessat(dfd, name, mode, flags);
}

SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
{
- return do_faccessat(AT_FDCWD, filename, mode, 0);
+ return do_faccessat(AT_FDCWD, getname(filename), mode, 0);
}

static int do_chdir(struct filename *name)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0205355bffb1bc..0c7672d3f1172f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3673,5 +3673,6 @@ static inline int inode_drain_writes(struct inode *inode)

int kern_chdir(const char *filename);
int kern_chroot(const char *filename);
+int __init kern_access(const char *filename, int mode);

#endif /* _LINUX_FS_H */
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index a3176d1a521467..b387e3700c68c5 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1326,13 +1326,6 @@ static inline int ksys_chmod(const char __user *filename, umode_t mode)
return do_fchmodat(AT_FDCWD, filename, mode);
}

-long do_faccessat(int dfd, const char __user *filename, int mode, int flags);
-
-static inline long ksys_access(const char __user *filename, int mode)
-{
- return do_faccessat(AT_FDCWD, filename, mode, 0);
-}
-
extern int do_fchownat(int dfd, const char __user *filename, uid_t user,
gid_t group, int flag);

diff --git a/init/main.c b/init/main.c
index c2c9143db96795..880f195b61abe1 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1514,8 +1514,7 @@ static noinline void __init kernel_init_freeable(void)
* check if there is an early userspace init. If yes, let it do all
* the work
*/
- if (ksys_access((const char __user *)
- ramdisk_execute_command, 0) != 0) {
+ if (kern_access(ramdisk_execute_command, 0) != 0) {
ramdisk_execute_command = NULL;
prepare_namespace();
}
--
2.27.0
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