| Message ID | 20220123100837.GA1491@haolee.io (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | proc: use kmalloc instead of __get_free_page() to alloc path buffer | expand |
On Sun, Jan 23, 2022 at 10:08:37AM +0000, Hao Lee wrote: > It's not a standard approach that use __get_free_page() to alloc path > buffer directly. We'd better use kmalloc and PATH_MAX. > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -1764,25 +1764,26 @@ static const char *proc_pid_get_link(struct dentry *dentry, > > static int do_proc_readlink(struct path *path, char __user *buffer, int buflen) > { > - char *tmp = (char *)__get_free_page(GFP_KERNEL); > + char *buf = NULL; I'd rather not rename anything but keep it minimal.
On Sun, Jan 23, 2022 at 10:08:37AM +0000, Hao Lee wrote: > It's not a standard approach that use __get_free_page() to alloc path > buffer directly. We'd better use kmalloc and PATH_MAX. If we're allocating PATH_MAX sized buffers for names, wouldn't it be suitable to use the name slab names_cachep declared in include/linux/fs.h using __getname() and __putname()? Best, Torin
diff --git a/fs/proc/base.c b/fs/proc/base.c index d654ce7150fd..74cfef87fe45 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1764,25 +1764,26 @@ static const char *proc_pid_get_link(struct dentry *dentry, static int do_proc_readlink(struct path *path, char __user *buffer, int buflen) { - char *tmp = (char *)__get_free_page(GFP_KERNEL); + char *buf = NULL; char *pathname; int len; - if (!tmp) + buf = kmalloc(PATH_MAX, GFP_KERNEL); + if (!buf) return -ENOMEM; - pathname = d_path(path, tmp, PAGE_SIZE); + pathname = d_path(path, buf, PATH_MAX); len = PTR_ERR(pathname); if (IS_ERR(pathname)) goto out; - len = tmp + PAGE_SIZE - 1 - pathname; + len = buf + PATH_MAX - 1 - pathname; if (len > buflen) len = buflen; if (copy_to_user(buffer, pathname, len)) len = -EFAULT; out: - free_page((unsigned long)tmp); + kfree(buf); return len; }
It's not a standard approach that use __get_free_page() to alloc path buffer directly. We'd better use kmalloc and PATH_MAX. Signed-off-by: Hao Lee <haolee.swjtu@gmail.com> --- fs/proc/base.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)