In exfat_nls_to_ucs2(), if there is no NLS loss and the char-to-ucs2 conversion is successfully completed, the variable "i" will have the same value as len.

However, exfat_nls_to_ucs2() checks p_cstring[i] to determine whether nls is lost immediately after the while loop ends, so if len is FSLABEL_MAX, "i" will also be FSLABEL_MAX immediately after the while loop ends, resulting in an out-of-bounds read of 1 byte from the p_cstring stack memory.

Therefore, to prevent this and properly determine whether nls has been lost, it should be modified to check if "i" and len are equal, rather than dereferencing p_cstring.

Cc: stable@vger.kernel.org Reported-by: syzbot+98cc76a76de46b3714d4@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=98cc76a76de46b3714d4 Fixes: 370e812b3ec1 ("exfat: add nls operations") Signed-off-by: Jeongjun Park aha310510@gmail.com --- fs/exfat/nls.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/exfat/nls.c b/fs/exfat/nls.c index 8243d94ceaf4..de06abe426d7 100644 --- a/fs/exfat/nls.c +++ b/fs/exfat/nls.c @@ -616,7 +616,7 @@ static int exfat_nls_to_ucs2(struct super_block *sb, unilen++; }

- if (p_cstring[i] != '\0') + if (i != len) lossy |= NLS_NAME_OVERLEN;

*uniname = '\0'; --