* Re: [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation [not found] ` <20170419103313.GA3238@e104818-lin.cambridge.arm.com> @ 2017-04-20 3:50 ` dongbo (E) 2017-04-20 3:50 ` dongbo (E) 0 siblings, 1 reply; 5+ messages in thread From: dongbo (E) @ 2017-04-20 3:50 UTC (permalink / raw) To: Catalin Marinas, Peter Maydell, linux Cc: Mark Rutland, Peter Maydell, Will Deacon, Linuxarm, linux-kernel@vger.kernel.org, Al Viro, linux-fsdevel, arm-mail-list, linux-arch On 2017/4/19 18:33, Catalin Marinas wrote: > On Tue, Apr 18, 2017 at 09:01:52PM +0100, Peter Maydell wrote: >> On 18 April 2017 at 18:01, Catalin Marinas <catalin.marinas@arm.com> wrote: >>> On Thu, Apr 13, 2017 at 08:33:52PM +0800, dongbo (E) wrote: >>>> From: Dong Bo <dongbo4@huawei.com> >>>> >>>> In load_elf_binary(), once the READ_IMPLIES_EXEC flag is set, >>>> the flag is propagated to its child processes, even the elf >>>> files are marked as not requiring executable stack. It may >>>> cause superfluous operations on some arch, e.g. >>>> __sync_icache_dcache on aarch64 due to a PROT_READ mmap is >>>> also marked as PROT_EXEC. >>>> >>>> Signed-off-by: Dong Bo <dongbo4@huawei.com> >>>> --- >>>> fs/binfmt_elf.c | 2 ++ >>>> fs/binfmt_elf_fdpic.c | 2 ++ >>>> 2 files changed, 4 insertions(+) >>>> >>>> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c >>>> index 5075fd5..c52e670 100644 >>>> --- a/fs/binfmt_elf.c >>>> +++ b/fs/binfmt_elf.c >>>> @@ -863,6 +863,8 @@ static int load_elf_binary(struct linux_binprm *bprm) >>>> SET_PERSONALITY2(loc->elf_ex, &arch_state); >>>> if (elf_read_implies_exec(loc->elf_ex, executable_stack)) >>>> current->personality |= READ_IMPLIES_EXEC; >>>> + else >>>> + current->personality &= ~READ_IMPLIES_EXEC; >>>> if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) >>>> current->flags |= PF_RANDOMIZE; >>>> diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c >>>> index cf93a4f..c4bc4d0 100644 >>>> --- a/fs/binfmt_elf_fdpic.c >>>> +++ b/fs/binfmt_elf_fdpic.c >>>> @@ -354,6 +354,8 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm) >>>> set_personality(PER_LINUX); >>>> if (elf_read_implies_exec(&exec_params.hdr, executable_stack)) >>>> current->personality |= READ_IMPLIES_EXEC; >>>> + else >>>> + current->personality &= ~READ_IMPLIES_EXEC; >>>> setup_new_exec(bprm); >> >>> That's affecting most architectures with a risk of ABI breakage. We >>> could do it on arm64 only, though I'm not yet clear on the ABI >>> implications (at a first look, there shouldn't be any). >> >> Is there a reason why it isn't just straightforwardly a bug >> (which we could fix) to make READ_IMPLIES_EXEC propagate to >> child processes? > > While I agree that it looks like a bug, if there are user programs > relying on such bug we call it "ABI". On arm64, I don't think there is > anything relying on inheriting READ_IMPLIES_EXEC but I wouldn't change > the compat task handling without the corresponding change in arch/arm. > With READ_IMPLIES_EXEC propagation, several hundreds times of __sync_icache_dcache operations shows up than not READ_IMPLIES_EXEC propagation, which degenerating the system performance. Changing arm64 only would settle our problem down, thanks for figuring out previously. Seems that arch/arm had discussed the propagation of READ_IMPLIES_EXEC: http://lists.infradead.org/pipermail/linux-arm-kernel/2012-February/086490.html But the READ_IMPLIES_EXEC is still not cleared in elf_set_personality(). >> AFAICT this should be per-process: just because >> init happens not to have been (re)compiled to permit non-executable >> stacks doesn't mean every process on the system needs to have >> an executable stack. > > I think this also affects the heap if brk(2) is used (via > VM_DATA_DEFAULT_FLAGS though I guess malloc mostly uses mmap these > days). > >> Behaviour shouldn't be variable across architectures either, I would >> hope. > > The behaviour has already been variable for a long time. Even on x86, > AFAICT x86_32 differs from x86_64 in this respect. > > Anyway, the patch should be posted to linux-arch for a cross-arch > discussion. > OK, this mail Cc to linux-arch. Thanks. ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation 2017-04-20 3:50 ` [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation dongbo (E) @ 2017-04-20 3:50 ` dongbo (E) 0 siblings, 0 replies; 5+ messages in thread From: dongbo (E) @ 2017-04-20 3:50 UTC (permalink / raw) To: Catalin Marinas, Peter Maydell, linux Cc: Mark Rutland, Peter Maydell, Will Deacon, Linuxarm, linux-kernel@vger.kernel.org, Al Viro, linux-fsdevel, arm-mail-list, linux-arch On 2017/4/19 18:33, Catalin Marinas wrote: > On Tue, Apr 18, 2017 at 09:01:52PM +0100, Peter Maydell wrote: >> On 18 April 2017 at 18:01, Catalin Marinas <catalin.marinas@arm.com> wrote: >>> On Thu, Apr 13, 2017 at 08:33:52PM +0800, dongbo (E) wrote: >>>> From: Dong Bo <dongbo4@huawei.com> >>>> >>>> In load_elf_binary(), once the READ_IMPLIES_EXEC flag is set, >>>> the flag is propagated to its child processes, even the elf >>>> files are marked as not requiring executable stack. It may >>>> cause superfluous operations on some arch, e.g. >>>> __sync_icache_dcache on aarch64 due to a PROT_READ mmap is >>>> also marked as PROT_EXEC. >>>> >>>> Signed-off-by: Dong Bo <dongbo4@huawei.com> >>>> --- >>>> fs/binfmt_elf.c | 2 ++ >>>> fs/binfmt_elf_fdpic.c | 2 ++ >>>> 2 files changed, 4 insertions(+) >>>> >>>> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c >>>> index 5075fd5..c52e670 100644 >>>> --- a/fs/binfmt_elf.c >>>> +++ b/fs/binfmt_elf.c >>>> @@ -863,6 +863,8 @@ static int load_elf_binary(struct linux_binprm *bprm) >>>> SET_PERSONALITY2(loc->elf_ex, &arch_state); >>>> if (elf_read_implies_exec(loc->elf_ex, executable_stack)) >>>> current->personality |= READ_IMPLIES_EXEC; >>>> + else >>>> + current->personality &= ~READ_IMPLIES_EXEC; >>>> if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) >>>> current->flags |= PF_RANDOMIZE; >>>> diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c >>>> index cf93a4f..c4bc4d0 100644 >>>> --- a/fs/binfmt_elf_fdpic.c >>>> +++ b/fs/binfmt_elf_fdpic.c >>>> @@ -354,6 +354,8 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm) >>>> set_personality(PER_LINUX); >>>> if (elf_read_implies_exec(&exec_params.hdr, executable_stack)) >>>> current->personality |= READ_IMPLIES_EXEC; >>>> + else >>>> + current->personality &= ~READ_IMPLIES_EXEC; >>>> setup_new_exec(bprm); >> >>> That's affecting most architectures with a risk of ABI breakage. We >>> could do it on arm64 only, though I'm not yet clear on the ABI >>> implications (at a first look, there shouldn't be any). >> >> Is there a reason why it isn't just straightforwardly a bug >> (which we could fix) to make READ_IMPLIES_EXEC propagate to >> child processes? > > While I agree that it looks like a bug, if there are user programs > relying on such bug we call it "ABI". On arm64, I don't think there is > anything relying on inheriting READ_IMPLIES_EXEC but I wouldn't change > the compat task handling without the corresponding change in arch/arm. > With READ_IMPLIES_EXEC propagation, several hundreds times of __sync_icache_dcache operations shows up than not READ_IMPLIES_EXEC propagation, which degenerating the system performance. Changing arm64 only would settle our problem down, thanks for figuring out previously. Seems that arch/arm had discussed the propagation of READ_IMPLIES_EXEC: http://lists.infradead.org/pipermail/linux-arm-kernel/2012-February/086490.html But the READ_IMPLIES_EXEC is still not cleared in elf_set_personality(). >> AFAICT this should be per-process: just because >> init happens not to have been (re)compiled to permit non-executable >> stacks doesn't mean every process on the system needs to have >> an executable stack. > > I think this also affects the heap if brk(2) is used (via > VM_DATA_DEFAULT_FLAGS though I guess malloc mostly uses mmap these > days). > >> Behaviour shouldn't be variable across architectures either, I would >> hope. > > The behaviour has already been variable for a long time. Even on x86, > AFAICT x86_32 differs from x86_64 in this respect. > > Anyway, the patch should be posted to linux-arch for a cross-arch > discussion. > OK, this mail Cc to linux-arch. Thanks. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH REPOST] fs: Preventing READ_IMPLIES_EXEC Propagation [not found] ` <2414e3b3-03f6-bd6c-5aa4-ad58c66b5aa5@huawei.com> [not found] ` <20170418170118.GH27592@e104818-lin.cambridge.arm.com> @ 2017-04-25 6:58 ` dongbo (E) 2017-06-12 13:41 ` Catalin Marinas 1 sibling, 1 reply; 5+ messages in thread From: dongbo (E) @ 2017-04-25 6:58 UTC (permalink / raw) To: linux-arch Cc: linux-fsdevel, Al Viro, linux-kernel@vger.kernel.org, catalin.marinas, will.deacon, arm-mail-list, Mark Rutland From: Dong Bo <dongbo4@huawei.com> In load_elf_binary(), once the READ_IMPLIES_EXEC flag is set, the flag is propagated to its child processes, even the elf files are marked as not requiring executable stack. It may cause superfluous operations on some arch, e.g. __sync_icache_dcache on aarch64 due to a PROT_READ mmap is also marked as PROT_EXEC. This patch was originally posted and discussed here: https://patchwork.kernel.org/patch/9685891/ Signed-off-by: Dong Bo <dongbo4@huawei.com> --- fs/binfmt_elf.c | 2 ++ fs/binfmt_elf_fdpic.c | 2 ++ 2 files changed, 4 insertions(+) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 5075fd5..c52e670 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -863,6 +863,8 @@ static int load_elf_binary(struct linux_binprm *bprm) SET_PERSONALITY2(loc->elf_ex, &arch_state); if (elf_read_implies_exec(loc->elf_ex, executable_stack)) current->personality |= READ_IMPLIES_EXEC; + else + current->personality &= ~READ_IMPLIES_EXEC; if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) current->flags |= PF_RANDOMIZE; diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c index cf93a4f..c4bc4d0 100644 --- a/fs/binfmt_elf_fdpic.c +++ b/fs/binfmt_elf_fdpic.c @@ -354,6 +354,8 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm) set_personality(PER_LINUX); if (elf_read_implies_exec(&exec_params.hdr, executable_stack)) current->personality |= READ_IMPLIES_EXEC; + else + current->personality &= ~READ_IMPLIES_EXEC; setup_new_exec(bprm); -- 1.9.1 . ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH REPOST] fs: Preventing READ_IMPLIES_EXEC Propagation 2017-04-25 6:58 ` [PATCH REPOST] " dongbo (E) @ 2017-06-12 13:41 ` Catalin Marinas 2017-06-12 13:41 ` Catalin Marinas 0 siblings, 1 reply; 5+ messages in thread From: Catalin Marinas @ 2017-06-12 13:41 UTC (permalink / raw) To: dongbo (E) Cc: linux-arch, linux-fsdevel, Al Viro, linux-kernel@vger.kernel.org, will.deacon, arm-mail-list, Mark Rutland On Tue, Apr 25, 2017 at 02:58:01PM +0800, dongbo (E) wrote: > From: Dong Bo <dongbo4@huawei.com> > > In load_elf_binary(), once the READ_IMPLIES_EXEC flag is set, > the flag is propagated to its child processes, even the elf > files are marked as not requiring executable stack. It may > cause superfluous operations on some arch, e.g. > __sync_icache_dcache on aarch64 due to a PROT_READ mmap is > also marked as PROT_EXEC. > > This patch was originally posted and discussed here: > https://patchwork.kernel.org/patch/9685891/ > > Signed-off-by: Dong Bo <dongbo4@huawei.com> > --- > fs/binfmt_elf.c | 2 ++ > fs/binfmt_elf_fdpic.c | 2 ++ > 2 files changed, 4 insertions(+) > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > index 5075fd5..c52e670 100644 > --- a/fs/binfmt_elf.c > +++ b/fs/binfmt_elf.c > @@ -863,6 +863,8 @@ static int load_elf_binary(struct linux_binprm *bprm) > SET_PERSONALITY2(loc->elf_ex, &arch_state); > if (elf_read_implies_exec(loc->elf_ex, executable_stack)) > current->personality |= READ_IMPLIES_EXEC; > + else > + current->personality &= ~READ_IMPLIES_EXEC; > if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) > current->flags |= PF_RANDOMIZE; > diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c > index cf93a4f..c4bc4d0 100644 > --- a/fs/binfmt_elf_fdpic.c > +++ b/fs/binfmt_elf_fdpic.c > @@ -354,6 +354,8 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm) > set_personality(PER_LINUX); > if (elf_read_implies_exec(&exec_params.hdr, executable_stack)) > current->personality |= READ_IMPLIES_EXEC; > + else > + current->personality &= ~READ_IMPLIES_EXEC; > setup_new_exec(bprm); > -- 1.9.1 FWIW, we queued the arm64-equivalent patch (commit 48f99c8ec0b25 in linux-next). It doesn't change the behaviour for compat tasks since we want to keep the same behaviour with arch/arm. If the above generic patch gets merged, we'll drop the arm64-specific one. -- Catalin ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH REPOST] fs: Preventing READ_IMPLIES_EXEC Propagation 2017-06-12 13:41 ` Catalin Marinas @ 2017-06-12 13:41 ` Catalin Marinas 0 siblings, 0 replies; 5+ messages in thread From: Catalin Marinas @ 2017-06-12 13:41 UTC (permalink / raw) To: dongbo (E) Cc: linux-arch, linux-fsdevel, Al Viro, linux-kernel@vger.kernel.org, will.deacon, arm-mail-list, Mark Rutland On Tue, Apr 25, 2017 at 02:58:01PM +0800, dongbo (E) wrote: > From: Dong Bo <dongbo4@huawei.com> > > In load_elf_binary(), once the READ_IMPLIES_EXEC flag is set, > the flag is propagated to its child processes, even the elf > files are marked as not requiring executable stack. It may > cause superfluous operations on some arch, e.g. > __sync_icache_dcache on aarch64 due to a PROT_READ mmap is > also marked as PROT_EXEC. > > This patch was originally posted and discussed here: > https://patchwork.kernel.org/patch/9685891/ > > Signed-off-by: Dong Bo <dongbo4@huawei.com> > --- > fs/binfmt_elf.c | 2 ++ > fs/binfmt_elf_fdpic.c | 2 ++ > 2 files changed, 4 insertions(+) > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > index 5075fd5..c52e670 100644 > --- a/fs/binfmt_elf.c > +++ b/fs/binfmt_elf.c > @@ -863,6 +863,8 @@ static int load_elf_binary(struct linux_binprm *bprm) > SET_PERSONALITY2(loc->elf_ex, &arch_state); > if (elf_read_implies_exec(loc->elf_ex, executable_stack)) > current->personality |= READ_IMPLIES_EXEC; > + else > + current->personality &= ~READ_IMPLIES_EXEC; > if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) > current->flags |= PF_RANDOMIZE; > diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c > index cf93a4f..c4bc4d0 100644 > --- a/fs/binfmt_elf_fdpic.c > +++ b/fs/binfmt_elf_fdpic.c > @@ -354,6 +354,8 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm) > set_personality(PER_LINUX); > if (elf_read_implies_exec(&exec_params.hdr, executable_stack)) > current->personality |= READ_IMPLIES_EXEC; > + else > + current->personality &= ~READ_IMPLIES_EXEC; > setup_new_exec(bprm); > -- 1.9.1 FWIW, we queued the arm64-equivalent patch (commit 48f99c8ec0b25 in linux-next). It doesn't change the behaviour for compat tasks since we want to keep the same behaviour with arch/arm. If the above generic patch gets merged, we'll drop the arm64-specific one. -- Catalin ^ permalink raw reply [flat|nested] 5+ messages in thread
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2017-04-20 3:50 ` [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation dongbo (E)
2017-04-20 3:50 ` dongbo (E)
2017-04-25 6:58 ` [PATCH REPOST] " dongbo (E)
2017-06-12 13:41 ` Catalin Marinas
2017-06-12 13:41 ` Catalin Marinas
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