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Message-ID: <20201019094355.4f6f3826@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> Date: Mon, 19 Oct 2020 09:43:55 -0700 From: Jakub Kicinski <kuba@...nel.org> To: laniel_francis@...vacyrequired.com Cc: linux-hardening@...r.kernel.org, davem@...emloft.net Subject: Re: [RFC][PATCH v2 2/3] Modify return value of nla_strlcpy to match that of strscpy. On Mon, 19 Oct 2020 17:23:30 +0200 laniel_francis@...vacyrequired.com wrote: > diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h > index d4d461236351..85f4ac779399 100644 > --- a/include/net/pkt_cls.h > +++ b/include/net/pkt_cls.h > @@ -4,6 +4,7 @@ > > #include <linux/pkt_cls.h> > #include <linux/workqueue.h> > +#include <linux/errno.h> Stray include. > #include <net/sch_generic.h> > #include <net/act_api.h> > #include <net/net_namespace.h> > diff --git a/lib/nlattr.c b/lib/nlattr.c > index 07156e581997..d692716bda78 100644 > --- a/lib/nlattr.c > +++ b/lib/nlattr.c > @@ -713,30 +713,39 @@ EXPORT_SYMBOL(nla_find); > * @dst: where to copy the string to > * @nla: attribute to copy the string from > * @dstsize: size of destination buffer > + * @returns: -E2BIG if @dstsize is 0 or source buffer length greater than I don't think this is correct format for kdoc. > + * @dstsize, otherwise it returns the number of copied characters (not > + * including the trailing %NUL). > * > * Copies at most dstsize - 1 bytes into the destination buffer. > - * The result is always a valid NUL-terminated string. Unlike > - * strlcpy the destination buffer is always padded out. > - * > - * Returns the length of the source buffer. > + * Unlike strlcpy the destination buffer is always padded out. > */ > -size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize) > +ssize_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize) > { > + size_t len; > + ssize_t ret; > size_t srclen = nla_len(nla); > char *src = nla_data(nla); Sort local variables long to short. > > + if (dstsize == 0 || WARN_ON_ONCE(dstsize > INT_MAX)) You can make it > U16_MAX, attr len is 16 bit. > + return -E2BIG; > + > if (srclen > 0 && src[srclen - 1] == '\0') > srclen--; > > - if (dstsize > 0) { > - size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen; > - > - memcpy(dst, src, len); > - /* Zero pad end of dst. */ > - memset(dst + len, 0, dstsize - len); > + if (srclen >= dstsize) { > + len = dstsize - 1; > + ret = -E2BIG; > + } else { > + len = srclen; > + ret = len; > } > > - return srclen; > + memcpy(dst, src, len); > + /* Zero pad end of dst. */ > + memset(dst + len, 0, dstsize - len); > + > + return ret; > } > EXPORT_SYMBOL(nla_strlcpy); > > diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c > index 41a55c6cbeb8..f0bf64393cbf 100644 > --- a/net/sched/cls_api.c > +++ b/net/sched/cls_api.c > @@ -223,7 +223,7 @@ static inline u32 tcf_auto_prio(struct tcf_proto *tp) > static bool tcf_proto_check_kind(struct nlattr *kind, char *name) > { > if (kind) > - return nla_strlcpy(name, kind, IFNAMSIZ) >= IFNAMSIZ; > + return nla_strlcpy(name, kind, IFNAMSIZ) > 0; Bug. > memset(name, 0, IFNAMSIZ); > return false; > }
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