Hi, On Thu, 2022-07-28 at 15:48 +0200, Mark Wielaard wrote: > With GCC 12.1.1, glibc 2.3a, -fsanitize=undefined and > -D_FORTIFY_SOURCE=3 we get the following error message: > > In file included from /usr/include/ar.h:22, > from ../libelf/libelfP.h:33, > from core-file.c:31: > In function ‘pread’, > inlined from ‘pread_retry’ at ../lib/system.h:188:21, > inlined from ‘elf_begin_rand’ at core-file.c:86:16, > inlined from ‘core_file_read_eagerly’ at core-file.c:205:15: > /usr/include/bits/unistd.h:74:10: error: ‘__pread_alias’ writing 58 > or more bytes into a region of size 10 overflows the destination [- > Werror=stringop-overflow=] > 74 | return __glibc_fortify (pread, __nbytes, sizeof (char), > | ^~~~~~~~~~~~~~~ > /usr/include/ar.h: In function ‘core_file_read_eagerly’: > /usr/include/ar.h:41:10: note: destination object ‘ar_size’ of size > 10 > 41 | char ar_size[10]; /* File size, in ASCII > decimal. */ > | ^~~~~~~ > /usr/include/bits/unistd.h:50:16: note: in a call to function > ‘__pread_alias’ declared with attribute ‘access (write_only, 2, 3)’ > 50 | extern ssize_t __REDIRECT (__pread_alias, > | ^~~~~~~~~~ > cc1: all warnings being treated as errors > > The warning disappears when dropping either -fsanitize=undefined > or when using -D_FORTIFY_SOURCE=2. It looks like a false positive. > But I haven't figured out how/why it happens. > > The code is a little tricky to proof correct though. The ar_size > field is a not-zero terminated string ASCII decimal, right-paddedr > with spaces. Which is then converted with strtoll. Relying on the > fact that the struct ar_hdr is zero initialized, so there will be > a zero byte after the ar_size field. > > Rewrite the code to just use a zero byte terminated char array. > Which is much easier to reason about. As a bonus the error > disappears.
The try build turned out green (ppc64le and s390x were red before) except for the centos7 builder where the native-biarch-core failed (this is a flaky test apparently because of a kernel issue dumping biarch cores?) An explicit rebuild made all tests PASS. So I have pushed this to get all our builders green again. Cheers, Mark
