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exfat: fix out-of-bounds in exfat_nls_to_ucs2() 

Since the len argument value passed to exfat_ioctl_set_volume_label()
from exfat_nls_to_utf16() is passed 1 too large, an out-of-bounds read
occurs when dereferencing p_cstring in exfat_nls_to_ucs2() later.

And because of the NLS_NAME_OVERLEN macro, another error occurs when
creating a file with a period at the end using utf8 and other iocharsets.

So to avoid this, you should remove the code that uses NLS_NAME_OVERLEN
macro and make the len argument value be the length of the label string,
but with a maximum length of FSLABEL_MAX - 1.

Reported-by: syzbot+98cc76a76de46b3714d4@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=98cc76a76de46b3714d4
Fixes: d01579d590 ("exfat: Add support for FS_IOC_{GET,SET}FSLABEL")
Suggested-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
pull/1354/merge
Jeongjun Park 2025-10-15 16:34:54 +09:00 committed by Namjae Jeon
parent 82ebecdc74
commit 2d8636119b
4 changed files with 5 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
fs/exfat/exfat_fs.h
View File

@ -29,7 +29,6 @@ enum exfat_error_mode {
enum { enum {
NLS_NAME_NO_LOSSY = 0, /* no lossy */ NLS_NAME_NO_LOSSY = 0, /* no lossy */
NLS_NAME_LOSSY = 1 << 0, /* just detected incorrect filename(s) */ NLS_NAME_LOSSY = 1 << 0, /* just detected incorrect filename(s) */
NLS_NAME_OVERLEN = 1 << 1, /* the length is over than its limit */
}; };
#define EXFAT_HASH_BITS 8 #define EXFAT_HASH_BITS 8

7
fs/exfat/file.c
View File

@ -509,8 +509,8 @@ static int exfat_ioctl_get_volume_label(struct super_block *sb, unsigned long ar
static int exfat_ioctl_set_volume_label(struct super_block *sb, static int exfat_ioctl_set_volume_label(struct super_block *sb,
unsigned long arg) unsigned long arg)
{ {
int ret = 0, lossy; int ret = 0, lossy, label_len;
char label[FSLABEL_MAX]; char label[FSLABEL_MAX] = {0};
struct exfat_uni_name uniname; struct exfat_uni_name uniname;
if (!capable(CAP_SYS_ADMIN)) if (!capable(CAP_SYS_ADMIN))
@ -520,8 +520,9 @@ static int exfat_ioctl_set_volume_label(struct super_block *sb,
return -EFAULT; return -EFAULT;
memset(&uniname, 0, sizeof(uniname)); memset(&uniname, 0, sizeof(uniname));
label_len = strnlen(label, FSLABEL_MAX - 1);
if (label[0]) { if (label[0]) {
ret = exfat_nls_to_utf16(sb, label, FSLABEL_MAX, ret = exfat_nls_to_utf16(sb, label, label_len,
&uniname, &lossy); &uniname, &lossy);
if (ret < 0) if (ret < 0)
return ret; return ret;

2
fs/exfat/namei.c
View File

@ -442,7 +442,7 @@ static int __exfat_resolve_path(struct inode *inode, const unsigned char *path,
return namelen; /* return error value */ return namelen; /* return error value */
if ((lossy && !lookup) || !namelen) if ((lossy && !lookup) || !namelen)
return (lossy & NLS_NAME_OVERLEN) ? -ENAMETOOLONG : -EINVAL; return -EINVAL;
return 0; return 0;
} }

3
fs/exfat/nls.c
View File

@ -616,9 +616,6 @@ static int exfat_nls_to_ucs2(struct super_block *sb,
unilen++; unilen++;
} }
if (p_cstring[i] != '\0')
lossy |= NLS_NAME_OVERLEN;
*uniname = '\0'; *uniname = '\0';
p_uniname->name_len = unilen; p_uniname->name_len = unilen;
p_uniname->name_hash = exfat_calc_chksum16(upname, unilen << 1, 0, p_uniname->name_hash = exfat_calc_chksum16(upname, unilen << 1, 0,