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On Wed, Dec 20, 2017 at 09:23:59PM +0100, Aurelien Jarno wrote: > The fillin_rpath function in elf/dl-load.c loops over each RPATH or > RUNPATH tokens and interprets 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). > > Fix that by moving the check for empty tokens before the dynamic string > token expansion. In addition, check for NULL pointer or empty strings > return by expand_dynamic_string_token. > > The above changes highlighted a bug in decompose_rpath, an empty array > is represented by the first element being NULL at the fillin_rpath > level, but by using a -1 pointer in decompose_rpath and other functions. > > Changelog: > [BZ #22625] > * elf/dl-load.c (fillin_rpath): Check for empty tokens before dynamic > string token expansion. Check for NULL pointer or empty string possibly > returned by expand_dynamic_string_token. > (decompose_rpath): Check for empty path after dynamic string > token expansion. > --- > ChangeLog | 10 ++++++++++ > NEWS | 4 ++++ > elf/dl-load.c | 35 ++++++++++++++++++++++++++--------- > 3 files changed, 40 insertions(+), 9 deletions(-) > > diff --git a/ChangeLog b/ChangeLog > index 35d1d102f6..0ed4d0ab15 100644 > --- a/ChangeLog > +++ b/ChangeLog > @@ -1,3 +1,13 @@ > +2017-12-20 Aurelien Jarno <aurelien@aurel32.net> > + Dmitry V. Levin <ldv@altlinux.org> > + > + [BZ #22625] > + * elf/dl-load.c (fillin_rpath): Check for empty tokens before dynamic > + string token expansion. Check for NULL pointer or empty string possibly > + returned by expand_dynamic_string_token. > + (decompose_rpath): Check for empty path after dynamic string > + token expansion. > + > 2017-12-20 Adhemerval Zanella <adhemerval.zanella@linaro.org> > > * nptl/Makefile (libpthread-routines): Add pthread_join_common. > 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 2964464158..955eb49ecb 100644 > --- a/elf/dl-load.c > +++ b/elf/dl-load.c > @@ -414,22 +414,31 @@ 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; > + char *to_free = NULL; > + size_t len = 0; > > - to_free = cp = expand_dynamic_string_token (l, cp, 1); > + /* `strsep' can pass an empty string. */ > + if (*cp != '\0') > + { > + to_free = cp = expand_dynamic_string_token (l, cp, 1); > > - size_t len = strlen (cp); > + /* expand_dynamic_string_token can return NULL in case of empty > + path or memory allocation failure. */ > + if (cp == NULL) > + continue; > > - /* `strsep' can pass an empty string. This has to be > - interpreted as `use the current directory'. */ > - if (len == 0) > - { > - static const char curwd[] = "./"; > - cp = (char *) curwd; > + /* Compute the length after dynamic string token expansion and > + ignore empty paths. */ > + len = strlen (cp); > + if (len == 0) > + { > + free (to_free); > + continue; > + } > } > > /* Remove trailing slashes (except for "/"). */ The longer I look at this hunk of fillin_rpath, the more I think that moving "Remove trailing slashes" and "Now add one" code inside "if (*cp != '\0')" statement will make fillin_rpath a bit more readable. -- ldv
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