From fabf5e49ddd61312027de8e92cc1b8528c2a929d Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Wed, 19 Jun 2019 10:13:50 +0200 Subject: [PATCH] dlfcn: Avoid one-element flexible array in Dl_serinfo [BZ #24166] The dls_serpath path field, as an array of length 1, introduces unexpected array subscript checks with some compilers. GCC versions before 3.0 treat the nested anonymous union as a declaration of an unnamed type, and not as a member declaration, so this construct cannot be used for these compilers. --- ChangeLog | 6 ++++++ dlfcn/dlfcn.h | 12 ++++++++++++ 2 files changed, 18 insertions(+) diff --git a/ChangeLog b/ChangeLog index ac06595fb4..f32b734166 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,9 @@ +2019-06-19 Florian Weimer + + [BZ #24166] + * dlfcn/dlfcn.h (Dl_serinfo): Do not use array of length 1 for + dls_serpath field. + 2019-06-18 Florian Weimer [BZ #24323] diff --git a/dlfcn/dlfcn.h b/dlfcn/dlfcn.h index 896ad6fc9b..c550371999 100644 --- a/dlfcn/dlfcn.h +++ b/dlfcn/dlfcn.h @@ -180,7 +180,19 @@ typedef struct { size_t dls_size; /* Size in bytes of the whole buffer. */ unsigned int dls_cnt; /* Number of elements in `dls_serpath'. */ +# if __GNUC_PREREQ (3, 0) + /* The zero-length array avoids an unwanted array subscript check by + the compiler, while the surrounding anonymous union preserves the + historic size of the type. At the time of writing, GNU C does + not support structs with flexible array members in unions. */ + __extension__ union + { + Dl_serpath dls_serpath[0]; /* Actually longer, dls_cnt elements. */ + Dl_serpath __dls_serpath_pad[1]; + }; +# else Dl_serpath dls_serpath[1]; /* Actually longer, dls_cnt elements. */ +# endif } Dl_serinfo; #endif /* __USE_GNU */