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Message-ID: <202307261545.E6827CBAD2@keescook>
Date: Wed, 26 Jul 2023 15:47:14 -0700
From: Kees Cook <keescook@...omium.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Mike Marshall <hubcap@...ibond.com>,
Martin Brandenburg <martin@...ibond.com>,
devel@...ts.orangefs.org, linux-kernel@...r.kernel.org,
Nathan Chancellor <nathan@...nel.org>
Subject: Re: [PATCH] orangefs: replace strncpy with strscpy
On Tue, Jul 25, 2023 at 03:29:10PM -0700, Justin Stitt wrote:
> On Tue, Jul 25, 2023 at 3:01 PM Kees Cook <keescook@...omium.org> wrote:
> >
> > On Tue, Jul 25, 2023 at 09:30:30PM +0000, justinstitt@...gle.com wrote:
> > > This patch aims to eliminate `strncpy` usage across the orangefs
> > > tree.
> > >
> > > `strncpy` is deprecated for use on NUL-terminated destination strings
> > > [1].
> > >
> > > A suitable replacement is `strscpy` [2].
> > >
> > > Using the `strscpy` api over `strncpy` has a slight wrinkle in the use
> > > cases presented within orangefs. There is frequent usage of `...LEN - 1`
> > > which is no longer required since `strscpy` will guarantee
> > > NUL-termination on its `dest` argument. As per `strscpy`s implementation
> > > in `linux/lib/string.c`
> > >
> > > | /* Hit buffer length without finding a NUL; force NUL-termination. */
> > > | if (res)
> > > | dest[res-1] = '\0';
> > >
> > > There are some hopes that someday the `strncpy` api could be ripped out
> > > due to the vast number of suitable replacements (strscpy, strscpy_pad,
> > > strtomem, strtomem_pad, strlcpy) [1].
> > >
> > > [1]: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
> > > [2]: manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
> > >
> > > ---
> > >
> > >
> > > Link: https://github.com/KSPP/linux/issues/90
> > > Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> > > ---
> > > fs/orangefs/dcache.c | 4 ++--
> > > fs/orangefs/namei.c | 30 +++++++++++++++---------------
> > > fs/orangefs/super.c | 14 +++++++-------
> > > 3 files changed, 24 insertions(+), 24 deletions(-)
> > >
> > > diff --git a/fs/orangefs/dcache.c b/fs/orangefs/dcache.c
> > > index 8bbe9486e3a6..96ed9900f7a9 100644
> > > --- a/fs/orangefs/dcache.c
> > > +++ b/fs/orangefs/dcache.c
> > > @@ -33,9 +33,9 @@ static int orangefs_revalidate_lookup(struct dentry *dentry)
> > >
> > > new_op->upcall.req.lookup.sym_follow = ORANGEFS_LOOKUP_LINK_NO_FOLLOW;
> > > new_op->upcall.req.lookup.parent_refn = parent->refn;
> > > - strncpy(new_op->upcall.req.lookup.d_name,
> > > + strscpy(new_op->upcall.req.lookup.d_name,
> > > dentry->d_name.name,
> > > - ORANGEFS_NAME_MAX - 1);
> > > + ORANGEFS_NAME_MAX);
> >
> > Looking where new_op comes from, I see that it was already zero-filled,
> > so this isn't also fixing a latent bug. (But I wanted to double-check.)
> >
> > >
> > > gossip_debug(GOSSIP_DCACHE_DEBUG,
> > > "%s:%s:%d interrupt flag [%d]\n",
> > > diff --git a/fs/orangefs/namei.c b/fs/orangefs/namei.c
> > > index 77518e248cf7..503d07769bb4 100644
> > > --- a/fs/orangefs/namei.c
> > > +++ b/fs/orangefs/namei.c
> > > @@ -41,8 +41,8 @@ static int orangefs_create(struct mnt_idmap *idmap,
> > > fill_default_sys_attrs(new_op->upcall.req.create.attributes,
> > > ORANGEFS_TYPE_METAFILE, mode);
> > >
> > > - strncpy(new_op->upcall.req.create.d_name,
> > > - dentry->d_name.name, ORANGEFS_NAME_MAX - 1);
> > > + strscpy(new_op->upcall.req.create.d_name,
> > > + dentry->d_name.name, ORANGEFS_NAME_MAX);
> > >
> > > ret = service_operation(new_op, __func__, get_interruptible_flag(dir));
> > >
> > > @@ -137,8 +137,8 @@ static struct dentry *orangefs_lookup(struct inode *dir, struct dentry *dentry,
> > > &parent->refn.khandle);
> > > new_op->upcall.req.lookup.parent_refn = parent->refn;
> > >
> > > - strncpy(new_op->upcall.req.lookup.d_name, dentry->d_name.name,
> > > - ORANGEFS_NAME_MAX - 1);
> > > + strscpy(new_op->upcall.req.lookup.d_name, dentry->d_name.name,
> > > + ORANGEFS_NAME_MAX);
> > >
> > > gossip_debug(GOSSIP_NAME_DEBUG,
> > > "%s: doing lookup on %s under %pU,%d\n",
> > > @@ -192,8 +192,8 @@ static int orangefs_unlink(struct inode *dir, struct dentry *dentry)
> > > return -ENOMEM;
> > >
> > > new_op->upcall.req.remove.parent_refn = parent->refn;
> > > - strncpy(new_op->upcall.req.remove.d_name, dentry->d_name.name,
> > > - ORANGEFS_NAME_MAX - 1);
> > > + strscpy(new_op->upcall.req.remove.d_name, dentry->d_name.name,
> > > + ORANGEFS_NAME_MAX);
> > >
> > > ret = service_operation(new_op, "orangefs_unlink",
> > > get_interruptible_flag(inode));
> > > @@ -247,10 +247,10 @@ static int orangefs_symlink(struct mnt_idmap *idmap,
> > > ORANGEFS_TYPE_SYMLINK,
> > > mode);
> > >
> > > - strncpy(new_op->upcall.req.sym.entry_name,
> > > + strscpy(new_op->upcall.req.sym.entry_name,
> > > dentry->d_name.name,
> > > - ORANGEFS_NAME_MAX - 1);
> > > - strncpy(new_op->upcall.req.sym.target, symname, ORANGEFS_NAME_MAX - 1);
> > > + ORANGEFS_NAME_MAX);
> > > + strscpy(new_op->upcall.req.sym.target, symname, ORANGEFS_NAME_MAX);
> > >
> > > ret = service_operation(new_op, __func__, get_interruptible_flag(dir));
> > >
> > > @@ -324,8 +324,8 @@ static int orangefs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
> > > fill_default_sys_attrs(new_op->upcall.req.mkdir.attributes,
> > > ORANGEFS_TYPE_DIRECTORY, mode);
> > >
> > > - strncpy(new_op->upcall.req.mkdir.d_name,
> > > - dentry->d_name.name, ORANGEFS_NAME_MAX - 1);
> > > + strscpy(new_op->upcall.req.mkdir.d_name,
> > > + dentry->d_name.name, ORANGEFS_NAME_MAX);
> > >
> > > ret = service_operation(new_op, __func__, get_interruptible_flag(dir));
> > >
> > > @@ -405,12 +405,12 @@ static int orangefs_rename(struct mnt_idmap *idmap,
> > > new_op->upcall.req.rename.old_parent_refn = ORANGEFS_I(old_dir)->refn;
> > > new_op->upcall.req.rename.new_parent_refn = ORANGEFS_I(new_dir)->refn;
> > >
> > > - strncpy(new_op->upcall.req.rename.d_old_name,
> > > + strscpy(new_op->upcall.req.rename.d_old_name,
> > > old_dentry->d_name.name,
> > > - ORANGEFS_NAME_MAX - 1);
> > > - strncpy(new_op->upcall.req.rename.d_new_name,
> > > + ORANGEFS_NAME_MAX);
> > > + strscpy(new_op->upcall.req.rename.d_new_name,
> > > new_dentry->d_name.name,
> > > - ORANGEFS_NAME_MAX - 1);
> > > + ORANGEFS_NAME_MAX);
> > >
> > > ret = service_operation(new_op,
> > > "orangefs_rename",
> > > diff --git a/fs/orangefs/super.c b/fs/orangefs/super.c
> > > index 5254256a224d..b4af98b5a216 100644
> > > --- a/fs/orangefs/super.c
> > > +++ b/fs/orangefs/super.c
> > > @@ -253,7 +253,7 @@ int orangefs_remount(struct orangefs_sb_info_s *orangefs_sb)
> > > new_op = op_alloc(ORANGEFS_VFS_OP_FS_MOUNT);
> > > if (!new_op)
> > > return -ENOMEM;
> > > - strncpy(new_op->upcall.req.fs_mount.orangefs_config_server,
> > > + strscpy(new_op->upcall.req.fs_mount.orangefs_config_server,
> > > orangefs_sb->devname,
> > > ORANGEFS_MAX_SERVER_ADDR_LEN);
> >
> > Was this a bug? (I think unreachable, both are
> > ORANGEFS_MAX_SERVER_ADDR_LEN long, but devname would already be
> > NUL-terminated.)
> >
> > Also, I wonder if all of these could be converted to:
> >
> > strscpy(dest, source, sizeof(dest))
> >
>
> I wonder if this idiom is a bit awkward in this context due to `dest`
> being quite a long series of struct accesses.
> For reference:
> | strncpy(new_op->upcall.req.fs_mount.orangefs_config_server,
> | orangefs_sb->devname,
> | sizeof(new_op->upcall.req.fs_mount.orangefs_config_server));
>
> The resolution would be creating a temp variable for the purposes of
> avoiding this long pattern. But that would mean it should probably be
> done for all instances like this.
>
> Is it worth it? Or is the long-winded sizeof(dest) OK?
I wouldn't add a variable. For this, let's skip the use of sizeof(). I
think in the future we might be able to do some kind of treewide change
to fix all of these.
>
>
> > Which (I think) would be a no-op change, and seems like a more robust
> > code style.
>
> >
> > >
> > > @@ -400,8 +400,8 @@ static int orangefs_unmount(int id, __s32 fs_id, const char *devname)
> > > return -ENOMEM;
> > > op->upcall.req.fs_umount.id = id;
> > > op->upcall.req.fs_umount.fs_id = fs_id;
> > > - strncpy(op->upcall.req.fs_umount.orangefs_config_server,
> > > - devname, ORANGEFS_MAX_SERVER_ADDR_LEN - 1);
> > > + strscpy(op->upcall.req.fs_umount.orangefs_config_server,
> > > + devname, ORANGEFS_MAX_SERVER_ADDR_LEN);
> > > r = service_operation(op, "orangefs_fs_umount", 0);
> > > /* Not much to do about an error here. */
> > > if (r)
> > > @@ -494,9 +494,9 @@ struct dentry *orangefs_mount(struct file_system_type *fst,
> > > if (!new_op)
> > > return ERR_PTR(-ENOMEM);
> > >
> > > - strncpy(new_op->upcall.req.fs_mount.orangefs_config_server,
> > > + strscpy(new_op->upcall.req.fs_mount.orangefs_config_server,
> > > devname,
> > > - ORANGEFS_MAX_SERVER_ADDR_LEN - 1);
> > > + ORANGEFS_MAX_SERVER_ADDR_LEN);
> > >
> > > gossip_debug(GOSSIP_SUPER_DEBUG,
> > > "Attempting ORANGEFS Mount via host %s\n",
> > > @@ -543,9 +543,9 @@ struct dentry *orangefs_mount(struct file_system_type *fst,
> > > * on successful mount, store the devname and data
> > > * used
> > > */
> > > - strncpy(ORANGEFS_SB(sb)->devname,
> > > + strscpy(ORANGEFS_SB(sb)->devname,
> > > devname,
> > > - ORANGEFS_MAX_SERVER_ADDR_LEN - 1);
> > > + ORANGEFS_MAX_SERVER_ADDR_LEN);
> > >
> > > /* mount_pending must be cleared */
> > > ORANGEFS_SB(sb)->mount_pending = 0;
> > >
> > > ---
> > > base-commit: 0b5547c51827e053cc754db47d3ec3e6c2c451d2
> > > change-id: 20230725-fs-orangefs-remove-deprecated-strncpy-ae0d40124620
> > >
> > > Best regards,
> > > --
> > > Justin Stitt <justinstitt@...gle.com>
> > >
> >
> > --
> > Kees Cook
>
>
>
> --
> Justin
--
Kees Cook
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