On Mon, Dec 31, 2018 at 05:34:25PM +0000, Andrew Cooper wrote: > A NT_GNU_BUILD_ID with namesz longer than 4 will cause the strncmp() to use > bytes in adjacent stringtable entries. > > Instead, check for namesz exactly equal to 4, and use memcmp() with an > explicit size. > > Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com> > --- > CC: Jan Beulich <jbeul...@suse.com> > CC: Wei Liu <wei.l...@citrix.com> > CC: Roger Pau Monné <roger....@citrix.com> > CC: Stefano Stabellini <sstabell...@kernel.org> > CC: Julien Grall <julien.gr...@arm.com> > > Noticed while auditing Xen's use of strncmp() for the command line patch. > --- > xen/common/version.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/xen/common/version.c b/xen/common/version.c > index 223cb52..1df7e78 100644 > --- a/xen/common/version.c > +++ b/xen/common/version.c > @@ -97,17 +97,17 @@ int xen_build_id_check(const Elf_Note *n, unsigned int > n_sz, > if ( NT_GNU_BUILD_ID != n->type ) > return -ENODATA; > > - if ( n->namesz + n->descsz < n->namesz ) > + if ( n->namesz != 4 /* GNU\0 */) > return -EINVAL; > > - if ( n->namesz < 4 /* GNU\0 */) > + if ( n->namesz + n->descsz < n->namesz )
The reordering of two predicates doesn't seem to serve any particular purpose? You could've just changed "<" to "!=" for less code churn? > return -EINVAL; > > if ( n->namesz + n->descsz > n_sz - sizeof(*n) ) > return -EINVAL; > > /* Sanity check, name should be "GNU" for ld-generated build-id. */ > - if ( strncmp(ELFNOTE_NAME(n), "GNU", n->namesz) != 0 ) > + if ( memcmp(ELFNOTE_NAME(n), "GNU", 4) != 0 ) OOI what is the advantage of memcmp compared to strncmp? Wei. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
