[v1] linux-user: Fix getdents alignment issues (#704)

[PATCH 2/4] linux-user: Always use flexible arrays for dirent d_name

Posted by Richard Henderson 4 years, 3 months ago

We currently use a flexible array member for target_dirent,
but use incorrectly fixed length arrays for target_dirent64,
linux_dirent and linux_dirent64.

This requires that we adjust the definition of the VFAT READDIR
ioctls which hard-code the 256 namelen size into the ioctl constant.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/syscall_defs.h | 6 +++---
 linux-user/syscall.c      | 6 ++++--
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
index a5ce487dcc..98b09ee6d6 100644
--- a/linux-user/syscall_defs.h
+++ b/linux-user/syscall_defs.h
@@ -441,7 +441,7 @@ struct target_dirent64 {
 	int64_t		d_off;
 	unsigned short	d_reclen;
 	unsigned char	d_type;
-	char		d_name[256];
+	char		d_name[];
 };
 
 
@@ -2714,7 +2714,7 @@ struct linux_dirent {
     long            d_ino;
     unsigned long   d_off;
     unsigned short  d_reclen;
-    char            d_name[256]; /* We must not include limits.h! */
+    char            d_name[];
 };
 
 struct linux_dirent64 {
@@ -2722,7 +2722,7 @@ struct linux_dirent64 {
     int64_t         d_off;
     unsigned short  d_reclen;
     unsigned char   d_type;
-    char            d_name[256];
+    char            d_name[];
 };
 
 struct target_mq_attr {
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index a2f605dec4..499415ad81 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -197,8 +197,10 @@
 //#define DEBUG_ERESTARTSYS
 
 //#include <linux/msdos_fs.h>
-#define	VFAT_IOCTL_READDIR_BOTH		_IOR('r', 1, struct linux_dirent [2])
-#define	VFAT_IOCTL_READDIR_SHORT	_IOR('r', 2, struct linux_dirent [2])
+#define VFAT_IOCTL_READDIR_BOTH \
+    _IOC(_IOC_READ, 'r', 1, (sizeof(struct linux_dirent) + 256) * 2)
+#define VFAT_IOCTL_READDIR_SHORT \
+    _IOC(_IOC_READ, 'r', 2, (sizeof(struct linux_dirent) + 256) * 2)
 
 #undef _syscall0
 #undef _syscall1
-- 
2.25.1

Re: [PATCH 2/4] linux-user: Always use flexible arrays for dirent d_name

Posted by Philippe Mathieu-Daudé 4 years, 3 months ago

On 11/7/21 13:48, Richard Henderson wrote:
> We currently use a flexible array member for target_dirent,
> but use incorrectly fixed length arrays for target_dirent64,
> linux_dirent and linux_dirent64.
> 
> This requires that we adjust the definition of the VFAT READDIR
> ioctls which hard-code the 256 namelen size into the ioctl constant.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  linux-user/syscall_defs.h | 6 +++---
>  linux-user/syscall.c      | 6 ++++--
>  2 files changed, 7 insertions(+), 5 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

Re: [PATCH 2/4] linux-user: Always use flexible arrays for dirent d_name

Posted by Warner Losh 4 years, 3 months ago


> On Nov 7, 2021, at 5:48 AM, Richard Henderson <richard.henderson@linaro.org> wrote:
> 
> We currently use a flexible array member for target_dirent,
> but use incorrectly fixed length arrays for target_dirent64,
> linux_dirent and linux_dirent64.
> 
> This requires that we adjust the definition of the VFAT READDIR
> ioctls which hard-code the 256 namelen size into the ioctl constant.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> linux-user/syscall_defs.h | 6 +++---
> linux-user/syscall.c      | 6 ++++--
> 2 files changed, 7 insertions(+), 5 deletions(-)

Reviewed by: Warner Losh <imp@bsdimp.com>


> diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
> index a5ce487dcc..98b09ee6d6 100644
> --- a/linux-user/syscall_defs.h
> +++ b/linux-user/syscall_defs.h
> @@ -441,7 +441,7 @@ struct target_dirent64 {
> 	int64_t		d_off;
> 	unsigned short	d_reclen;
> 	unsigned char	d_type;
> -	char		d_name[256];
> +	char		d_name[];
> };
> 
> 
> @@ -2714,7 +2714,7 @@ struct linux_dirent {
>     long            d_ino;
>     unsigned long   d_off;
>     unsigned short  d_reclen;
> -    char            d_name[256]; /* We must not include limits.h! */
> +    char            d_name[];
> };
> 
> struct linux_dirent64 {
> @@ -2722,7 +2722,7 @@ struct linux_dirent64 {
>     int64_t         d_off;
>     unsigned short  d_reclen;
>     unsigned char   d_type;
> -    char            d_name[256];
> +    char            d_name[];
> };
> 
> struct target_mq_attr {
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index a2f605dec4..499415ad81 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -197,8 +197,10 @@
> //#define DEBUG_ERESTARTSYS
> 
> //#include <linux/msdos_fs.h>
> -#define	VFAT_IOCTL_READDIR_BOTH		_IOR('r', 1, struct linux_dirent [2])
> -#define	VFAT_IOCTL_READDIR_SHORT	_IOR('r', 2, struct linux_dirent [2])
> +#define VFAT_IOCTL_READDIR_BOTH \
> +    _IOC(_IOC_READ, 'r', 1, (sizeof(struct linux_dirent) + 256) * 2)
> +#define VFAT_IOCTL_READDIR_SHORT \
> +    _IOC(_IOC_READ, 'r', 2, (sizeof(struct linux_dirent) + 256) * 2)
> 
> #undef _syscall0
> #undef _syscall1
> -- 
> 2.25.1
> 
>