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On 2017-12-19 00:16, Dmitry V. Levin wrote: > On Mon, Dec 18, 2017 at 09:42:13PM +0100, Aurelien Jarno wrote: > > The fillin_rpath function in elf/dl-load.c loops over each RPATH or > > RUNPATH tokens and intepret empty tokens as the current directory > > ("./"). In practice the check for empty token is done *after* the > > dynamic string token expansion. The expansion process can return an > > empty string for the $ORIGIN token if __libc_enable_secure is set > > or if the path of the binary can not be determined (/proc not mounted). > > > > To fix that, move the check for empty tokens before the dynamic string > > token expansion. Change expand_dynamic_string_token to return NULL > > instead of an empty string, and check for NULL pointer returned by > > expand_dynamic_string_token. > > > > The above changed highlighted a bug in decompose_rpath, an empty array > > is represented by the first element being NULL at the fillin_rpath path > > level, but by using a -1 pointer in decompose_rpath and other functions. > > > > Changelog: > > [BZ #22625] > > * elf/dl-load.c (expand_dynamic_string_token): Return NULL instead > > of an empty string. > > (fillin_rpath): Check for empty tokens before dynamic string token > > expansion. Check for NULL pointer possibly returned by > > expand_dynamic_string_token. > > (decompose_rpath): Check for empty path after dynamic string > > token expansion. > > --- > > ChangeLog | 12 ++++++++++++ > > NEWS | 4 ++++ > > elf/dl-load.c | 43 ++++++++++++++++++++++++++++++++++++------- > > 3 files changed, 52 insertions(+), 7 deletions(-) > > > > > > This new version includes the suggestions done by Dmitry. It would be > > nice if it could be reviewed by at least one more person, especially > > the part modifying expand_dynamic_string_token. > > > > diff --git a/ChangeLog b/ChangeLog > > index 4a7164354f..24a5223485 100644 > > --- a/ChangeLog > > +++ b/ChangeLog > > @@ -1,3 +1,15 @@ > > +2017-12-17 Aurelien Jarno <aurelien@aurel32.net> > > + Dmitry V. Levin <ldv@altlinux.org> > > + > > + [BZ #22625] > > + * elf/dl-load.c (expand_dynamic_string_token): Return NULL instead > > + of an empty string. > > + (fillin_rpath): Check for empty tokens before dynamic string token > > + expansion. Check for NULL pointer possibly returned by > > + expand_dynamic_string_token. > > + (decompose_rpath): Check for empty path after dynamic string > > + token expansion. > > + > > 2017-12-18 Sergei Trofimovich <slyfox@gentoo.org> > > > > [BZ #22624] > > diff --git a/NEWS b/NEWS > > index a43ff26e83..0d43e93a17 100644 > > --- a/NEWS > > +++ b/NEWS > > @@ -149,6 +149,10 @@ Security related changes: > > CVE-2017-1000366 has been applied, but it is mentioned here only because > > of the CVE assignment.) Reported by Qualys. > > > > + CVE-2017-16997: Incorrect handling of RPATH or RUNPATH containing $ORIGIN > > + for AT_SECURE or SUID binaries could be used to load libraries from the > > + current directory. > > + > > The following bugs are resolved with this release: > > > > [The release manager will add the list generated by > > diff --git a/elf/dl-load.c b/elf/dl-load.c > > index e7d97dcc56..827ec1c491 100644 > > --- a/elf/dl-load.c > > +++ b/elf/dl-load.c > > @@ -384,7 +384,17 @@ expand_dynamic_string_token (struct link_map *l, const char *s, int is_path) > > if (result == NULL) > > return NULL; > > > > - return _dl_dst_substitute (l, s, result, is_path); > > + char *retval = _dl_dst_substitute (l, s, result, is_path); > > + > > + /* If substitution of dynamic string tokens resulted to an empty string, > > + return NULL as in case of insufficient memory. */ > > + if (__glibc_unlikely (*retval == '\0')) > > + { > > + free (result); > > + return NULL; > > + } > > + > > + return retval; > > } > > > > > > @@ -433,22 +443,33 @@ fillin_rpath (char *rpath, struct r_search_path_elem **result, const char *sep, > > { > > char *cp; > > size_t nelems = 0; > > - char *to_free; > > > > while ((cp = __strsep (&rpath, sep)) != NULL) > > { > > struct r_search_path_elem *dirp; > > - > > - to_free = cp = expand_dynamic_string_token (l, cp, 1); > > - > > - size_t len = strlen (cp); > > + char *to_free = NULL; > > + size_t len; > > > > /* `strsep' can pass an empty string. This has to be > > interpreted as `use the current directory'. */ > > - if (len == 0) > > + if (*cp == '\0') > > { > > static const char curwd[] = "./"; > > cp = (char *) curwd; > > + len = 0; > > + } > > + else > > + { > > + to_free = cp = expand_dynamic_string_token (l, cp, 1); > > + > > + /* expand_dynamic_string_token can return NULL in case of empty > > + path or memory allocation failure. */ > > + if (cp == NULL) > > + continue; > > + > > + /* Recompute the length after dynamic string token expansion > > + and ignore empty paths. */ > > Just /* Compute the length after dynamic string token expansion. */ Good catch, I have fixed that locally. > > > + len = strlen (cp); > > } > > > > /* Remove trailing slashes (except for "/"). */ > > @@ -620,6 +641,14 @@ decompose_rpath (struct r_search_path_struct *sps, > > necessary. */ > > free (copy); > > > > + /* There is no path after expansion. */ > > + if (result[0] == NULL) > > + { > > + free (result); > > + sps->dirs = (struct r_search_path_elem **) -1; > > + return false; > > + } > > + > > sps->dirs = result; > > /* The caller will change this value if we haven't used a real malloc. */ > > sps->malloced = 1; > > I think the patch is fine. > Thanks for the review, let's see if someone else has comments on it. -- Aurelien Jarno GPG: 4096R/1DDD8C9B aurelien@aurel32.net http://www.aurel32.net
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