ext4: use memtostr_pad() for s_volume_name

As with the other strings in struct ext4_super_block, s_volume_name is
not NUL terminated. The other strings were marked in commit 072ebb3bffe6
("ext4: add nonstring annotations to ext4.h"). Using strscpy() isn't
the right replacement for strncpy(); it should use memtostr_pad()
instead.

Reported-by: syzbot+50835f73143cc2905b9e@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/00000000000019f4c00619192c05@google.com/
Fixes: 744a56389f73 ("ext4: replace deprecated strncpy with alternatives")
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://patch.msgid.link/20240523225408.work.904-kees@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 983dad8c07ecd1b4123c2217d0e7b22b7b7519cd..efed7f09876de91048f7614b9ed7294a30c4d56f 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1347,7 +1347,7 @@ struct ext4_super_block {
 /*60*/ __le32  s_feature_incompat;     /* incompatible feature set */
        __le32  s_feature_ro_compat;    /* readonly-compatible feature set */
 /*68*/ __u8    s_uuid[16];             /* 128-bit uuid for volume */
-/*78*/ char    s_volume_name[EXT4_LABEL_MAX];  /* volume name */
+/*78*/ char    s_volume_name[EXT4_LABEL_MAX] __nonstring; /* volume name */
 /*88*/ char    s_last_mounted[64] __nonstring; /* directory where last mounted */
 /*C8*/ __le32  s_algorithm_usage_bitmap; /* For compression */
        /*

diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index dab7acd497092369ef8b3a7e677a300de55269e0..e8bf5972dd47bf6db227981fa753ea304fcef85e 100644 (file)
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -1151,7 +1151,7 @@ static int ext4_ioctl_getlabel(struct ext4_sb_info *sbi, char __user *user_label
        BUILD_BUG_ON(EXT4_LABEL_MAX >= FSLABEL_MAX);
 
        lock_buffer(sbi->s_sbh);
-       strscpy_pad(label, sbi->s_es->s_volume_name);
+       memtostr_pad(label, sbi->s_es->s_volume_name);
        unlock_buffer(sbi->s_sbh);
 
        if (copy_to_user(user_label, label, sizeof(label)))