| Message ID | Ye1fCxyZZ0I5lgOL@localhost.localdomain (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] proc: alloc PATH_MAX bytes for /proc/${pid}/fd/ symlinks | expand |
On Sun, Jan 23, 2022 at 9:58 PM Alexey Dobriyan <adobriyan@gmail.com> wrote: > > From: Hao Lee <haolee.swjtu@gmail.com> > > It's not a standard approach that use __get_free_page() to alloc path > buffer directly. We'd better use kmalloc and PATH_MAX. > > PAGE_SIZE is different on different archs. This is indeed a worthy addition. Thanks. Regards, Hao Lee > An unlinked file > with very long canonical pathname will readlink differently > because "(deleted)" eats into a buffer. --adobriyan > > Signed-off-by: Hao Lee <haolee.swjtu@gmail.com> > Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> > --- > > fs/proc/base.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -1764,25 +1764,25 @@ 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 *tmp = (char *)kmalloc(PATH_MAX, GFP_KERNEL); > char *pathname; > int len; > > if (!tmp) > return -ENOMEM; > > - pathname = d_path(path, tmp, PAGE_SIZE); > + pathname = d_path(path, tmp, PATH_MAX); > len = PTR_ERR(pathname); > if (IS_ERR(pathname)) > goto out; > - len = tmp + PAGE_SIZE - 1 - pathname; > + len = tmp + 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(tmp); > return len; > } >
--- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1764,25 +1764,25 @@ 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 *tmp = (char *)kmalloc(PATH_MAX, GFP_KERNEL); char *pathname; int len; if (!tmp) return -ENOMEM; - pathname = d_path(path, tmp, PAGE_SIZE); + pathname = d_path(path, tmp, PATH_MAX); len = PTR_ERR(pathname); if (IS_ERR(pathname)) goto out; - len = tmp + PAGE_SIZE - 1 - pathname; + len = tmp + 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(tmp); return len; }