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Message-ID: <39b2d8af-812f-8c5e-3957-34543add0173@broadcom.com>
Date: Fri, 17 Jul 2020 12:04:18 -0700
From: Scott Branden <scott.branden@...adcom.com>
To: Kees Cook <keescook@...omium.org>
Cc: Mimi Zohar <zohar@...ux.ibm.com>,
Matthew Wilcox <willy@...radead.org>,
James Morris <jmorris@...ei.org>,
Luis Chamberlain <mcgrof@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Jessica Yu <jeyu@...nel.org>,
Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
"Serge E. Hallyn" <serge@...lyn.com>,
Casey Schaufler <casey@...aufler-ca.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Peter Zijlstra <peterz@...radead.org>,
Matthew Garrett <matthewgarrett@...gle.com>,
David Howells <dhowells@...hat.com>,
Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
Randy Dunlap <rdunlap@...radead.org>,
"Joel Fernandes (Google)" <joel@...lfernandes.org>,
KP Singh <kpsingh@...gle.com>, Dave Olsthoorn <dave@...aar.me>,
Hans de Goede <hdegoede@...hat.com>,
Peter Jones <pjones@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Stephen Boyd <stephen.boyd@...aro.org>,
Paul Moore <paul@...l-moore.com>,
Stephen Smalley <stephen.smalley.work@...il.com>,
linux-security-module@...r.kernel.org,
linux-integrity@...r.kernel.org, selinux@...r.kernel.org,
linux-fsdevel@...r.kernel.org, kexec@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/13] fs/kernel_read_file: Remove redundant size argument
Hi Kees,
On 2020-07-17 10:43 a.m., Kees Cook wrote:
> In preparation for refactoring kernel_read_file*(), remove the redundant
> "size" argument which is not needed: it can be included in the return
I don't think the size argument is redundant though.
The existing kernel_read_file functions always read the whole file.
Now, what happens if the file is bigger than the buffer.
How does kernel_read_file know it read the whole file by looking at the
return value?
> code, with callers adjusted. (VFS reads already cannot be larger than
> INT_MAX.)
>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> drivers/base/firmware_loader/main.c | 8 ++++----
> fs/kernel_read_file.c | 20 +++++++++-----------
> include/linux/kernel_read_file.h | 8 ++++----
> kernel/kexec_file.c | 13 ++++++-------
> kernel/module.c | 7 +++----
> security/integrity/digsig.c | 5 +++--
> security/integrity/ima/ima_fs.c | 5 +++--
> 7 files changed, 32 insertions(+), 34 deletions(-)
>
> diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
> index d4a413ea48ce..ea419c7d3d34 100644
> --- a/drivers/base/firmware_loader/main.c
> +++ b/drivers/base/firmware_loader/main.c
> @@ -462,7 +462,7 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
> size_t in_size,
> const void *in_buffer))
> {
> - loff_t size;
> + size_t size;
> int i, len;
> int rc = -ENOENT;
> char *path;
> @@ -494,10 +494,9 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
> fw_priv->size = 0;
>
> /* load firmware files from the mount namespace of init */
> - rc = kernel_read_file_from_path_initns(path, &buffer,
> - &size, msize,
> + rc = kernel_read_file_from_path_initns(path, &buffer, msize,
> READING_FIRMWARE);
> - if (rc) {
> + if (rc < 0) {
> if (rc != -ENOENT)
> dev_warn(device, "loading %s failed with error %d\n",
> path, rc);
> @@ -506,6 +505,7 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
> path);
> continue;
> }
> + size = rc;
> dev_dbg(device, "Loading firmware from %s\n", path);
> if (decompress) {
> dev_dbg(device, "f/w decompressing %s\n",
> diff --git a/fs/kernel_read_file.c b/fs/kernel_read_file.c
> index 54d972d4befc..dc28a8def597 100644
> --- a/fs/kernel_read_file.c
> +++ b/fs/kernel_read_file.c
> @@ -5,7 +5,7 @@
> #include <linux/security.h>
> #include <linux/vmalloc.h>
>
> -int kernel_read_file(struct file *file, void **buf, loff_t *size,
> +int kernel_read_file(struct file *file, void **buf,
> loff_t max_size, enum kernel_read_file_id id)
> {
> loff_t i_size, pos;
> @@ -29,7 +29,7 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,
> ret = -EINVAL;
> goto out;
> }
> - if (i_size > SIZE_MAX || (max_size > 0 && i_size > max_size)) {
> + if (i_size > INT_MAX || (max_size > 0 && i_size > max_size)) {
Should this be SSIZE_MAX?
> ret = -EFBIG;
> goto out;
> }
> @@ -59,8 +59,6 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,
> }
>
> ret = security_kernel_post_read_file(file, *buf, i_size, id);
> - if (!ret)
> - *size = pos;
>
> out_free:
> if (ret < 0) {
> @@ -72,11 +70,11 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,
>
> out:
> allow_write_access(file);
> - return ret;
> + return ret == 0 ? pos : ret;
> }
> EXPORT_SYMBOL_GPL(kernel_read_file);
>
> -int kernel_read_file_from_path(const char *path, void **buf, loff_t *size,
> +int kernel_read_file_from_path(const char *path, void **buf,
> loff_t max_size, enum kernel_read_file_id id)
> {
> struct file *file;
> @@ -89,14 +87,14 @@ int kernel_read_file_from_path(const char *path, void **buf, loff_t *size,
> if (IS_ERR(file))
> return PTR_ERR(file);
>
> - ret = kernel_read_file(file, buf, size, max_size, id);
> + ret = kernel_read_file(file, buf, max_size, id);
> fput(file);
> return ret;
> }
> EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
>
> int kernel_read_file_from_path_initns(const char *path, void **buf,
> - loff_t *size, loff_t max_size,
> + loff_t max_size,
> enum kernel_read_file_id id)
> {
> struct file *file;
> @@ -115,13 +113,13 @@ int kernel_read_file_from_path_initns(const char *path, void **buf,
> if (IS_ERR(file))
> return PTR_ERR(file);
>
> - ret = kernel_read_file(file, buf, size, max_size, id);
> + ret = kernel_read_file(file, buf, max_size, id);
> fput(file);
> return ret;
> }
> EXPORT_SYMBOL_GPL(kernel_read_file_from_path_initns);
>
> -int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
> +int kernel_read_file_from_fd(int fd, void **buf, loff_t max_size,
> enum kernel_read_file_id id)
> {
> struct fd f = fdget(fd);
> @@ -130,7 +128,7 @@ int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
> if (!f.file)
> goto out;
>
> - ret = kernel_read_file(f.file, buf, size, max_size, id);
> + ret = kernel_read_file(f.file, buf, max_size, id);
> out:
> fdput(f);
> return ret;
> diff --git a/include/linux/kernel_read_file.h b/include/linux/kernel_read_file.h
> index 78cf3d7dc835..0ca0bdbed1bd 100644
> --- a/include/linux/kernel_read_file.h
> +++ b/include/linux/kernel_read_file.h
> @@ -36,16 +36,16 @@ static inline const char *kernel_read_file_id_str(enum kernel_read_file_id id)
> }
>
> int kernel_read_file(struct file *file,
> - void **buf, loff_t *size, loff_t max_size,
> + void **buf, loff_t max_size,
> enum kernel_read_file_id id);
> int kernel_read_file_from_path(const char *path,
> - void **buf, loff_t *size, loff_t max_size,
> + void **buf, loff_t max_size,
> enum kernel_read_file_id id);
> int kernel_read_file_from_path_initns(const char *path,
> - void **buf, loff_t *size, loff_t max_size,
> + void **buf, loff_t max_size,
> enum kernel_read_file_id id);
> int kernel_read_file_from_fd(int fd,
> - void **buf, loff_t *size, loff_t max_size,
> + void **buf, loff_t max_size,
> enum kernel_read_file_id id);
>
> #endif /* _LINUX_KERNEL_READ_FILE_H */
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index 1358069ce9e9..a201bbb19158 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -220,13 +220,12 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
> {
> int ret;
> void *ldata;
> - loff_t size;
>
> ret = kernel_read_file_from_fd(kernel_fd, &image->kernel_buf,
> - &size, INT_MAX, READING_KEXEC_IMAGE);
> - if (ret)
> + INT_MAX, READING_KEXEC_IMAGE);
> + if (ret < 0)
> return ret;
> - image->kernel_buf_len = size;
> + image->kernel_buf_len = ret;
>
> /* Call arch image probe handlers */
> ret = arch_kexec_kernel_image_probe(image, image->kernel_buf,
> @@ -243,11 +242,11 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
> /* It is possible that there no initramfs is being loaded */
> if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
> ret = kernel_read_file_from_fd(initrd_fd, &image->initrd_buf,
> - &size, INT_MAX,
> + INT_MAX,
> READING_KEXEC_INITRAMFS);
> - if (ret)
> + if (ret < 0)
> goto out;
> - image->initrd_buf_len = size;
> + image->initrd_buf_len = ret;
> }
>
> if (cmdline_len) {
> diff --git a/kernel/module.c b/kernel/module.c
> index e9765803601b..b6fd4f51cc30 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3988,7 +3988,6 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
> SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
> {
> struct load_info info = { };
> - loff_t size;
> void *hdr = NULL;
> int err;
>
> @@ -4002,12 +4001,12 @@ SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
> |MODULE_INIT_IGNORE_VERMAGIC))
> return -EINVAL;
>
> - err = kernel_read_file_from_fd(fd, &hdr, &size, INT_MAX,
> + err = kernel_read_file_from_fd(fd, &hdr, INT_MAX,
> READING_MODULE);
> - if (err)
> + if (err < 0)
> return err;
> info.hdr = hdr;
> - info.len = size;
> + info.len = err;
>
> return load_module(&info, uargs, flags);
> }
> diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
> index f8869be45d8f..97661ffabc4e 100644
> --- a/security/integrity/digsig.c
> +++ b/security/integrity/digsig.c
> @@ -171,16 +171,17 @@ int __init integrity_add_key(const unsigned int id, const void *data,
> int __init integrity_load_x509(const unsigned int id, const char *path)
> {
> void *data = NULL;
> - loff_t size;
> + size_t size;
> int rc;
> key_perm_t perm;
>
> - rc = kernel_read_file_from_path(path, &data, &size, 0,
> + rc = kernel_read_file_from_path(path, &data, 0,
> READING_X509_CERTIFICATE);
> if (rc < 0) {
> pr_err("Unable to open file: %s (%d)", path, rc);
> return rc;
> }
> + size = rc;
>
> perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ;
>
> diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
> index e13ffece3726..9ba145d3d6d9 100644
> --- a/security/integrity/ima/ima_fs.c
> +++ b/security/integrity/ima/ima_fs.c
> @@ -275,7 +275,7 @@ static ssize_t ima_read_policy(char *path)
> {
> void *data = NULL;
> char *datap;
> - loff_t size;
> + size_t size;
> int rc, pathlen = strlen(path);
>
> char *p;
> @@ -284,11 +284,12 @@ static ssize_t ima_read_policy(char *path)
> datap = path;
> strsep(&datap, "\n");
>
> - rc = kernel_read_file_from_path(path, &data, &size, 0, READING_POLICY);
> + rc = kernel_read_file_from_path(path, &data, 0, READING_POLICY);
> if (rc < 0) {
> pr_err("Unable to open file: %s (%d)", path, rc);
> return rc;
> }
> + size = rc;
>
> datap = data;
> while (size > 0 && (p = strsep(&datap, "\n"))) {
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