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Date: Thu, 28 Mar 2024 20:54:25 -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, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] orangefs: cleanup uses of strncpy
On Fri, Mar 22, 2024 at 09:41:18PM +0000, Justin Stitt wrote:
> strncpy() is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
>
> There is some care taken to ensure these destination buffers are
> NUL-terminated by bounding the strncpy()'s by ORANGEFS_NAME_MAX - 1 or
> ORANGEFS_MAX_SERVER_ADDR_LEN - 1. Instead, we can use the new 2-argument
> version of strscpy() to guarantee NUL-termination on the destination
> buffers while simplifying the code.
>
> Based on usage with printf-likes, we can see these buffers are expected
> to be NUL-terminated:
> | gossip_debug(GOSSIP_NAME_DEBUG,
> | "%s: doing lookup on %s under %pU,%d\n",
> | __func__,
> | new_op->upcall.req.lookup.d_name,
> | &new_op->upcall.req.lookup.parent_refn.khandle,
> | new_op->upcall.req.lookup.parent_refn.fs_id);
> ...
> | gossip_debug(GOSSIP_SUPER_DEBUG,
> | "Attempting ORANGEFS Remount via host %s\n",
> | new_op->upcall.req.fs_mount.orangefs_config_server);
>
> NUL-padding isn't required for any of these destination buffers as
> they've all been zero-allocated with op_alloc() or kzalloc().
>
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> ---
> Note: build-tested only.
>
> Found with: $ rg "strncpy\("
> ---
> fs/orangefs/dcache.c | 4 +---
> fs/orangefs/namei.c | 26 ++++++++------------------
> fs/orangefs/super.c | 17 ++++++-----------
> 3 files changed, 15 insertions(+), 32 deletions(-)
>
> diff --git a/fs/orangefs/dcache.c b/fs/orangefs/dcache.c
> index 8bbe9486e3a6..395a00ed8ac7 100644
> --- a/fs/orangefs/dcache.c
> +++ b/fs/orangefs/dcache.c
> @@ -33,9 +33,7 @@ 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,
> - dentry->d_name.name,
> - ORANGEFS_NAME_MAX - 1);
> + strscpy(new_op->upcall.req.lookup.d_name, dentry->d_name.name);
>
> 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 c9dfd5c6a097..200558ec72f0 100644
> --- a/fs/orangefs/namei.c
> +++ b/fs/orangefs/namei.c
> @@ -41,8 +41,7 @@ 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);
>
> ret = service_operation(new_op, __func__, get_interruptible_flag(dir));
>
> @@ -137,8 +136,7 @@ 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);
>
> gossip_debug(GOSSIP_NAME_DEBUG,
> "%s: doing lookup on %s under %pU,%d\n",
> @@ -192,8 +190,7 @@ 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);
>
> ret = service_operation(new_op, "orangefs_unlink",
> get_interruptible_flag(inode));
> @@ -247,10 +244,8 @@ static int orangefs_symlink(struct mnt_idmap *idmap,
> ORANGEFS_TYPE_SYMLINK,
> mode);
>
> - strncpy(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);
> + strscpy(new_op->upcall.req.sym.entry_name, dentry->d_name.name);
> + strscpy(new_op->upcall.req.sym.target, symname);
>
> ret = service_operation(new_op, __func__, get_interruptible_flag(dir));
>
> @@ -324,8 +319,7 @@ 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);
>
> ret = service_operation(new_op, __func__, get_interruptible_flag(dir));
>
> @@ -405,12 +399,8 @@ 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,
> - old_dentry->d_name.name,
> - ORANGEFS_NAME_MAX - 1);
> - strncpy(new_op->upcall.req.rename.d_new_name,
> - new_dentry->d_name.name,
> - ORANGEFS_NAME_MAX - 1);
> + strscpy(new_op->upcall.req.rename.d_old_name, old_dentry->d_name.name);
> + strscpy(new_op->upcall.req.rename.d_new_name, new_dentry->d_name.name);
>
> ret = service_operation(new_op,
> "orangefs_rename",
> diff --git a/fs/orangefs/super.c b/fs/orangefs/super.c
> index 34849b4a3243..fb4d09c2f531 100644
> --- a/fs/orangefs/super.c
> +++ b/fs/orangefs/super.c
> @@ -253,9 +253,8 @@ 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,
> - orangefs_sb->devname,
> - ORANGEFS_MAX_SERVER_ADDR_LEN);
> + strscpy(new_op->upcall.req.fs_mount.orangefs_config_server,
> + orangefs_sb->devname);
This one place doesn't use "ORANGEFS_MAX_SERVER_ADDR_LEN - 1", but this
appears to be an existing (likely unreachable) bug.
Reviewed-by: Kees Cook <keescook@...omium.org>
-Kees
>
> gossip_debug(GOSSIP_SUPER_DEBUG,
> "Attempting ORANGEFS Remount via host %s\n",
> @@ -400,8 +399,7 @@ 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);
> r = service_operation(op, "orangefs_fs_umount", 0);
> /* Not much to do about an error here. */
> if (r)
> @@ -494,9 +492,7 @@ 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,
> - devname,
> - ORANGEFS_MAX_SERVER_ADDR_LEN - 1);
> + strscpy(new_op->upcall.req.fs_mount.orangefs_config_server, devname);
>
> gossip_debug(GOSSIP_SUPER_DEBUG,
> "Attempting ORANGEFS Mount via host %s\n",
> @@ -543,9 +539,8 @@ struct dentry *orangefs_mount(struct file_system_type *fst,
> * on successful mount, store the devname and data
> * used
> */
> - strncpy(ORANGEFS_SB(sb)->devname,
> - devname,
> - ORANGEFS_MAX_SERVER_ADDR_LEN - 1);
> + strscpy(ORANGEFS_SB(sb)->devname, devname);
> +
>
> /* mount_pending must be cleared */
> ORANGEFS_SB(sb)->mount_pending = 0;
>
> ---
> base-commit: 241590e5a1d1b6219c8d3045c167f2fbcc076cbb
> change-id: 20240322-strncpy-fs-orangefs-dcache-c-9a0cf2d22dae
>
> Best regards,
> --
> Justin Stitt <justinstitt@...gle.com>
>
>
--
Kees Cook
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