diff mbox series

[06/13] fs/kernel_read_file: Remove redundant size argument

Message ID 20200717174309.1164575-7-keescook@chromium.org
State New
Headers show
Series Introduce partial kernel_read_file() support | expand

Commit Message

Kees Cook July 17, 2020, 5:43 p.m. UTC
In preparation for refactoring kernel_read_file*(), remove the redundant
"size" argument which is not needed: it can be included in the return
code, with callers adjusted. (VFS reads already cannot be larger than
INT_MAX.)

Signed-off-by: Kees Cook <keescook@chromium.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(-)

Comments

Scott Branden July 17, 2020, 7:04 p.m. UTC | #1
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@chromium.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"))) {
Scott Branden July 17, 2020, 7:55 p.m. UTC | #2
On 2020-07-17 12:04 p.m., Scott Branden wrote:
> 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?
Actually, this change looks ok dealing with the size.  I'll look at the 
rest.
>
>> code, with callers adjusted. (VFS reads already cannot be larger than
>> INT_MAX.)
>>
>> Signed-off-by: Kees Cook <keescook@chromium.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"))) {
>
Kees Cook July 17, 2020, 10:06 p.m. UTC | #3
On Fri, Jul 17, 2020 at 12:04:18PM -0700, Scott Branden wrote:
> 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?

Yes; an entirely reasonable concern. This is why I add the file_size
output argument later in the series.

> > code, with callers adjusted. (VFS reads already cannot be larger than
> > INT_MAX.)
> > [...]
> > -	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?

No, for two reasons: then we need to change the return value and likely
the callers need more careful checks, and more importantly, because the
VFS already limits single read actions to INT_MAX, so limits above this
make no sense. Win win! :)
Scott Branden July 18, 2020, 5:44 a.m. UTC | #4
Hi Kees,

On 2020-07-17 3:06 p.m., Kees Cook wrote:
> On Fri, Jul 17, 2020 at 12:04:18PM -0700, Scott Branden wrote:
>> 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?
> Yes; an entirely reasonable concern. This is why I add the file_size
> output argument later in the series.
There is something wrong with this patch.  I apply patches 1-5 and these 
pass the kernel self test.
Patch 6 does not pass the kernel-selftest/firmware/fw_run_tests.sh

>>> code, with callers adjusted. (VFS reads already cannot be larger than
>>> INT_MAX.)
>>> [...]
>>> -	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?
> No, for two reasons: then we need to change the return value and likely
> the callers need more careful checks, and more importantly, because the
> VFS already limits single read actions to INT_MAX, so limits above this
> make no sense. Win win! :)
>
Scott Branden July 21, 2020, 9:43 p.m. UTC | #5
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
> code, with callers adjusted. (VFS reads already cannot be larger than
> INT_MAX.)
>
> Signed-off-by: Kees Cook <keescook@chromium.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;
Change fails to return 0.  Need rc = 0; here.
>   		dev_dbg(device, "Loading firmware from %s\n", path);
>   		if (decompress) {
>   			dev_dbg(device, "f/w decompressing %s\n",
>
Kees Cook July 21, 2020, 9:50 p.m. UTC | #6
On Tue, Jul 21, 2020 at 02:43:07PM -0700, Scott Branden wrote:
> 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
> > code, with callers adjusted. (VFS reads already cannot be larger than
> > INT_MAX.)
> > 
> > Signed-off-by: Kees Cook <keescook@chromium.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;
> Change fails to return 0.  Need rc = 0; here.

Oh nice; good catch! I'll fix this.
diff mbox series

Patch

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)) {
 		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"))) {