* ldd not working on ET_EXEC executables @ 2016-12-06 1:39 Laine Gholson 2016-12-06 2:33 ` Rich Felker 0 siblings, 1 reply; 5+ messages in thread From: Laine Gholson @ 2016-12-06 1:39 UTC (permalink / raw) To: musl Hello, I am running musl on a ARM platform, and ldd won't work on a executable with the ET_EXEC type. running GNU ld 2.25.1, gcc 6.2.0, and musl 1.1.15-git-71-g54991729 $ gcc -fPIE -pie test.c -o test-pie $ ldd test-pie <no error> $ gcc -fno-PIE -no-pie test.c -o test-nopie $ ldd test-nopie ldd: test-nopie: Not a valid dynamic program $ elfedit --output-type DYN test-nopie $ ldd test-nopie <no error> Any idea why ldd says executables with the ET_EXEC type aren't valid? ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: ldd not working on ET_EXEC executables 2016-12-06 1:39 ldd not working on ET_EXEC executables Laine Gholson @ 2016-12-06 2:33 ` Rich Felker 2016-12-08 22:30 ` Laine Gholson 0 siblings, 1 reply; 5+ messages in thread From: Rich Felker @ 2016-12-06 2:33 UTC (permalink / raw) To: musl On Mon, Dec 05, 2016 at 07:39:32PM -0600, Laine Gholson wrote: > Hello, > > I am running musl on a ARM platform, and ldd won't work on a executable with the ET_EXEC type. > > running GNU ld 2.25.1, gcc 6.2.0, and musl 1.1.15-git-71-g54991729 > > $ gcc -fPIE -pie test.c -o test-pie > $ ldd test-pie > <no error> > $ gcc -fno-PIE -no-pie test.c -o test-nopie > $ ldd test-nopie > ldd: test-nopie: Not a valid dynamic program > $ elfedit --output-type DYN test-nopie > $ ldd test-nopie > <no error> > > Any idea why ldd says executables with the ET_EXEC type aren't valid? strace it; I suspect you'll find that mmap is not honoring the requested address. This is a bug introduced intentionally by grsec/pax and perhaps other hardened kernels. Rich ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: ldd not working on ET_EXEC executables 2016-12-06 2:33 ` Rich Felker @ 2016-12-08 22:30 ` Laine Gholson 2016-12-08 22:41 ` Rich Felker 0 siblings, 1 reply; 5+ messages in thread From: Laine Gholson @ 2016-12-08 22:30 UTC (permalink / raw) To: musl You mean RANDMMAP? PaX's RANDMMAP feature ignoring the address your requesting it (without MAP_FIXED) is perfectly valid, to quote POSIX: "When MAP_FIXED is not set, the implementation uses addr in an implementation-defined manner to arrive at pa." mmap2(0x10000, 73728, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0x1234abcd You're not passing MAP_FIXED to mmap() but are expecting the kernel to still use the address you're giving it, which is wrong. (as a side note, glibc works and it uses MAP_FIXED) Thanks, Laine Gholson On 12/05/16 20:33, Rich Felker wrote: > On Mon, Dec 05, 2016 at 07:39:32PM -0600, Laine Gholson wrote: >> Hello, >> >> I am running musl on a ARM platform, and ldd won't work on a executable with the ET_EXEC type. >> >> running GNU ld 2.25.1, gcc 6.2.0, and musl 1.1.15-git-71-g54991729 >> >> $ gcc -fPIE -pie test.c -o test-pie >> $ ldd test-pie >> <no error> >> $ gcc -fno-PIE -no-pie test.c -o test-nopie >> $ ldd test-nopie >> ldd: test-nopie: Not a valid dynamic program >> $ elfedit --output-type DYN test-nopie >> $ ldd test-nopie >> <no error> >> >> Any idea why ldd says executables with the ET_EXEC type aren't valid? > > strace it; I suspect you'll find that mmap is not honoring the > requested address. This is a bug introduced intentionally by grsec/pax > and perhaps other hardened kernels. > > Rich > ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: ldd not working on ET_EXEC executables 2016-12-08 22:30 ` Laine Gholson @ 2016-12-08 22:41 ` Rich Felker 2016-12-09 0:05 ` Shiz 0 siblings, 1 reply; 5+ messages in thread From: Rich Felker @ 2016-12-08 22:41 UTC (permalink / raw) To: musl On Thu, Dec 08, 2016 at 04:30:42PM -0600, Laine Gholson wrote: > You mean RANDMMAP? PaX's RANDMMAP feature ignoring the address your requesting it (without MAP_FIXED) is perfectly valid, to quote POSIX: > "When MAP_FIXED is not set, the implementation uses addr in an implementation-defined manner to arrive at pa." > mmap2(0x10000, 73728, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0x1234abcd It's _valid_, but it's a bad implementation choice; it makes it impossible to request a particular range, which is necessary for ldso/ldd to load non-PIE programs. > You're not passing MAP_FIXED to mmap() but are expecting the kernel to still use the address you're giving it, which is wrong. > (as a side note, glibc works and it uses MAP_FIXED) This is invalid, and a bug in glibc, as there's no way to know that you're not mapping over something that's already there (perhaps even the function that's calling mmap). You can only use MAP_FIXED to map over top of an existing mapping you already know about and intend to replace (same with dup2 and file descriptors), not an arbitrary address range. Rich > Thanks, > > Laine Gholson > > On 12/05/16 20:33, Rich Felker wrote: > >On Mon, Dec 05, 2016 at 07:39:32PM -0600, Laine Gholson wrote: > >>Hello, > >> > >>I am running musl on a ARM platform, and ldd won't work on a executable with the ET_EXEC type. > >> > >>running GNU ld 2.25.1, gcc 6.2.0, and musl 1.1.15-git-71-g54991729 > >> > >> $ gcc -fPIE -pie test.c -o test-pie > >> $ ldd test-pie > >><no error> > >> $ gcc -fno-PIE -no-pie test.c -o test-nopie > >> $ ldd test-nopie > >>ldd: test-nopie: Not a valid dynamic program > >> $ elfedit --output-type DYN test-nopie > >> $ ldd test-nopie > >><no error> > >> > >>Any idea why ldd says executables with the ET_EXEC type aren't valid? > > > >strace it; I suspect you'll find that mmap is not honoring the > >requested address. This is a bug introduced intentionally by grsec/pax > >and perhaps other hardened kernels. > > > >Rich > > ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: ldd not working on ET_EXEC executables 2016-12-08 22:41 ` Rich Felker @ 2016-12-09 0:05 ` Shiz 0 siblings, 0 replies; 5+ messages in thread From: Shiz @ 2016-12-09 0:05 UTC (permalink / raw) To: musl > On 8 Dec 2016, at 23:41, Rich Felker <dalias@libc.org> wrote: > > On Thu, Dec 08, 2016 at 04:30:42PM -0600, Laine Gholson wrote: >> You mean RANDMMAP? PaX's RANDMMAP feature ignoring the address your requesting it (without MAP_FIXED) is perfectly valid, to quote POSIX: >> "When MAP_FIXED is not set, the implementation uses addr in an implementation-defined manner to arrive at pa." >> mmap2(0x10000, 73728, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0x1234abcd > > It's _valid_, but it's a bad implementation choice; it makes it > impossible to request a particular range, which is necessary for > ldso/ldd to load non-PIE programs. Good. Position-dependent executables should not be used or supported. - Shiz ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2016-12-09 0:05 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2016-12-06 1:39 ldd not working on ET_EXEC executables Laine Gholson 2016-12-06 2:33 ` Rich Felker 2016-12-08 22:30 ` Laine Gholson 2016-12-08 22:41 ` Rich Felker 2016-12-09 0:05 ` Shiz
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