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Date: Wed, 18 Aug 2021 09:21:57 -0400 From: Jeff Layton <jlayton@...nel.org> To: Len Baker <len.baker@....com>, Steve French <sfrench@...ba.org>, Suresh Jayaraman <sjayaraman@...e.de> Cc: linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org, linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>, linux-hardening@...r.kernel.org Subject: Re: [PATCH] CIFS: Fix a potencially linear read overflow On Tue, 2021-08-17 at 12:27 +0200, Len Baker wrote: > strlcpy() reads the entire source buffer first. This read may exceed the > destination size limit. This is both inefficient and can lead to linear > read overflows if a source string is not NUL-terminated. > > Also, the strnlen() call does not avoid the read overflow in the strlcpy > function when a not NUL-terminated string is passed. > > So, replace this block by a call to kstrndup() that avoids this type of > overflow and does the same. > > Fixes: 066ce6899484d ("cifs: rename cifs_strlcpy_to_host and make it use new functions") > Signed-off-by: Len Baker <len.baker@....com> > --- > fs/cifs/cifs_unicode.c | 9 ++------- > 1 file changed, 2 insertions(+), 7 deletions(-) > > diff --git a/fs/cifs/cifs_unicode.c b/fs/cifs/cifs_unicode.c > index 9bd03a231032..171ad8b42107 100644 > --- a/fs/cifs/cifs_unicode.c > +++ b/fs/cifs/cifs_unicode.c > @@ -358,14 +358,9 @@ cifs_strndup_from_utf16(const char *src, const int maxlen, > if (!dst) > return NULL; > cifs_from_utf16(dst, (__le16 *) src, len, maxlen, codepage, > - NO_MAP_UNI_RSVD); > + NO_MAP_UNI_RSVD); > } else { > - len = strnlen(src, maxlen); > - len++; > - dst = kmalloc(len, GFP_KERNEL); > - if (!dst) > - return NULL; > - strlcpy(dst, src, len); > + dst = kstrndup(src, maxlen, GFP_KERNEL); > } > > return dst; > -- > 2.25.1 > Reviewed-by: Jeff Layton <jlayton@...nel.org>
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