On Mon 13-11-17 10:20:06, Michal Hocko wrote: > [Cc arm and ppc maintainers]
Hmm, it turned out to be a problem on other architectures as well. CCing more maintainers. For your reference, we are talking about http://lkml.kernel.org/r/20171023082608.6167-1-mho...@kernel.org which has broken architectures which do apply aligning on the mmap address hint without MAP_FIXED applied. See below my proposed way around this issue because I belive that the above patch is quite valuable on its own to be dropped for all archs. > Thanks a lot for testing! > > On Sun 12-11-17 11:38:02, Joel Stanley wrote: > > On Fri, Nov 10, 2017 at 11:00 PM, Michal Hocko <mho...@kernel.org> wrote: > > > Hi Joel, > > > > > > On Wed 08-11-17 15:20:50, Michal Hocko wrote: > > > [...] > > >> > There are a lot of messages on the way up that look like this: > > >> > > > >> > [ 2.527460] Uhuuh, elf segement at 000d9000 requested but the > > >> > memory is mapped already > > >> > [ 2.540160] Uhuuh, elf segement at 000d9000 requested but the > > >> > memory is mapped already > > >> > [ 2.546153] Uhuuh, elf segement at 000d9000 requested but the > > >> > memory is mapped already > > >> > > > >> > And then trying to run userspace looks like this: > > >> > > >> Could you please run with debugging patch posted > > >> http://lkml.kernel.org/r/20171107102854.vylrtaodla63k...@dhcp22.suse.cz > > > > > > Did you have chance to test with this debugging patch, please? > > > > Lots of this: > > > > [ 1.177266] Uhuuh, elf segement at 000d9000 requested but the memory is > > mapped already, got 000dd000 > > [ 1.177555] Clashing vma [dd000, de000] flags:100873 name:(null) > > This smells like the problem I've expected that mmap with hint doesn't > respect the hint even though there is no clashing mapping. The above > basically says that we didn't map at 0xd9000 but it has placed it at > 0xdd000. The nearest (clashing) vma is at 0xdd000 so this is our new > mapping. find_vma returns the closest vma (with addr < vm_end) for the > given address 0xd9000 so this address cannot be mapped by any other vma. > > Now that I am looking at arm's arch_get_unmapped_area it does perform > aligning for shared vmas. We do not do that for MAP_FIXED. Powepc, > reported earlier [1] seems to suffer from the similar problem. > slice_get_unmapped_area alignes to slices, whatever that means. > > I can see two possible ways around that. Either we explicitly request > non-aligned mappings via a special MAP_$FOO (e.g. MAP_FIXED_SAFE) or > simply opt out from the MAP_FIXED protection via ifdefs. The first > option sounds more generic to me but also more tricky to not introduce > other user visible effects. The later is quite straightforward. What do > you think about the following on top of the previous patch? > > It is rather terse and disables the MAP_FIXED protection for arm > comletely because I couldn't find a way to make it conditional on > CACHEID_VIPT_ALIASING. But this can be always handled later. I find the > protection for other archtectures useful enough to have this working for > most architectures now and handle others specially. > > [1] http://lkml.kernel.org/r/1510048229.12079.7.ca...@abdul.in.ibm.com > --- diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 61a0cb15067e..018d041a30e6 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -99,6 +99,7 @@ config ARM select PERF_USE_VMALLOC select RTC_LIB select SYS_SUPPORTS_APM_EMULATION + select ARCH_ALIGNED_MMAPS # Above selects are sorted alphabetically; please add new ones # according to that. Thanks. help diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index 48d91d5be4e9..eca59d27e9f1 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -72,6 +72,7 @@ config MIPS select RTC_LIB if !MACH_LOONGSON64 select SYSCTL_EXCEPTION_TRACE select VIRT_TO_BUS + select ARCH_ALIGNED_MMAPS menu "Machine selection" diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig index 22f27ec8c117..8376d16e0a4a 100644 --- a/arch/parisc/Kconfig +++ b/arch/parisc/Kconfig @@ -40,6 +40,7 @@ config PARISC select GENERIC_CLOCKEVENTS select ARCH_NO_COHERENT_DMA_MMAP select CPU_NO_EFFICIENT_FFS + select ARCH_ALIGNED_MMAPS help The PA-RISC microprocessor is designed by Hewlett-Packard and used diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype index 2f629e0551e9..156f69c09c7f 100644 --- a/arch/powerpc/platforms/Kconfig.cputype +++ b/arch/powerpc/platforms/Kconfig.cputype @@ -368,6 +368,7 @@ config PPC_MM_SLICES bool default y if PPC_STD_MMU_64 default n + select ARCH_ALIGNED_MMAPS config PPC_HAVE_PMU_SUPPORT bool diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig index 640a85925060..ac1d4637a728 100644 --- a/arch/sh/Kconfig +++ b/arch/sh/Kconfig @@ -49,6 +49,7 @@ config SUPERH select HAVE_ARCH_AUDITSYSCALL select HAVE_FUTEX_CMPXCHG if FUTEX select HAVE_NMI + select ARCH_ALIGNED_MMAPS help The SuperH is a RISC processor targeted for use in embedded systems and consumer electronics; it was also used in the Sega Dreamcast diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig index 0be3828752e5..c265dcda3d28 100644 --- a/arch/sparc/Kconfig +++ b/arch/sparc/Kconfig @@ -45,6 +45,7 @@ config SPARC select CPU_NO_EFFICIENT_FFS select LOCKDEP_SMALL if LOCKDEP select ARCH_WANT_RELAX_ORDER + select ARCH_ALIGNED_MMAPS if SPARC64 config SPARC32 def_bool !64BIT diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig index 7ad6d77b2f22..a5cf535034d1 100644 --- a/arch/xtensa/Kconfig +++ b/arch/xtensa/Kconfig @@ -30,6 +30,7 @@ config XTENSA select NO_BOOTMEM select PERF_USE_VMALLOC select VIRT_TO_BUS + select ARCH_ALIGNED_MMAPS if MMU help Xtensa processors are 32-bit RISC machines designed by Tensilica primarily for embedded systems. These processors are both diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index a22718de42db..d23eb89f31c0 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -345,13 +345,19 @@ static unsigned long elf_vm_mmap(struct file *filep, unsigned long addr, unsigned long size, int prot, int type, unsigned long off) { unsigned long map_addr; + unsigned long map_type = type; /* * If caller requests the mapping at a specific place, make sure we fail * rather than potentially clobber an existing mapping which can have - * security consequences (e.g. smash over the stack area). + * security consequences (e.g. smash over the stack area). Be careful + * about architectures which do not respect the address hint due to + * aligning restrictions for !fixed mappings. */ - map_addr = vm_mmap(filep, addr, size, prot, type & ~MAP_FIXED, off); + if (!IS_ENABLED(ARCH_ALIGNED_MMAPS)) + map_type &= ~MAP_FIXED; + + map_addr = vm_mmap(filep, addr, size, prot, map_type, off); if (BAD_ADDR(map_addr)) return map_addr; -- Michal Hocko SUSE Labs
