| Message ID | 20100209154141.03F0.A69D9226@jp.fujitsu.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
In message <20100209154141.03F0.A69D9226@jp.fujitsu.com> you wrote: > > When reserving stack space for a new process, make sure we're not > > attempting to expand the stack by more than rlimit allows. > > > > This fixes a bug caused by b6a2fea39318e43fee84fa7b0b90d68bed92d2ba "mm: > > variable length argument support" and unmasked by > > fc63cf237078c86214abcb2ee9926d8ad289da9b "exec: setup_arg_pages() fails > > to return errors". This bug means when limiting the stack to less the > > 20*PAGE_SIZE (eg. 80K on 4K pages or 'ulimit -s 79') all processes will > > be killed before they start. This is particularly bad with 64K pages, > > where a ulimit below 1280K will kill every process. > > > > Signed-off-by: Michael Neuling <mikey@neuling.org> > > Cc: stable@kernel.org > > --- > > Attempts to answer comments from Kosaki Motohiro. > > > > Tested on PPC only, hence !CONFIG_STACK_GROWSUP. Someone should > > probably ACK for an arch with CONFIG_STACK_GROWSUP. > > > > As noted, stable needs the same patch, but 2.6.32 doesn't have the > > rlimit() helper. > > > > fs/exec.c | 21 ++++++++++++++++++--- > > 1 file changed, 18 insertions(+), 3 deletions(-) > > > > Index: linux-2.6-ozlabs/fs/exec.c > > =================================================================== > > --- linux-2.6-ozlabs.orig/fs/exec.c > > +++ linux-2.6-ozlabs/fs/exec.c > > @@ -555,6 +555,7 @@ static int shift_arg_pages(struct vm_are > > } > > > > #define EXTRA_STACK_VM_PAGES 20 /* random */ > > +#define ALIGN_DOWN(addr,size) ((addr)&(~((size)-1))) > > > > /* > > * Finalizes the stack vm_area_struct. The flags and permissions are updat ed, > > @@ -570,7 +571,7 @@ int setup_arg_pages(struct linux_binprm > > struct vm_area_struct *vma = bprm->vma; > > struct vm_area_struct *prev = NULL; > > unsigned long vm_flags; > > - unsigned long stack_base; > > + unsigned long stack_base, stack_expand, stack_expand_lim, stack_size; > > > > #ifdef CONFIG_STACK_GROWSUP > > /* Limit stack size to 1GB */ > > @@ -627,10 +628,24 @@ int setup_arg_pages(struct linux_binprm > > goto out_unlock; > > } > > > > + stack_expand = EXTRA_STACK_VM_PAGES * PAGE_SIZE; > > + stack_size = vma->vm_end - vma->vm_start; > > + if (rlimit(RLIMIT_STACK) < stack_size) > > + stack_expand_lim = 0; /* don't shrick the stack */ > > + else > > + /* > > + * Align this down to a page boundary as expand_stack > > + * will align it up. > > + */ > > + stack_expand_lim = ALIGN_DOWN(rlimit(RLIMIT_STACK) - stack_size , > > + PAGE_SIZE); > > + /* Initial stack must not cause stack overflow. */ > > + if (stack_expand > stack_expand_lim) > > + stack_expand = stack_expand_lim; > > #ifdef CONFIG_STACK_GROWSUP > > - stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE; > > + stack_base = vma->vm_end + stack_expand; > > #else > > - stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE; > > + stack_base = vma->vm_start - stack_expand; > > #endif > > ret = expand_stack(vma, stack_base); > > if (ret) > > Umm.. It looks correct. but the nested complex if statement seems a bit ugly. > Instead, How about following? I don't like the duplicated code in the #ifdef/else but I can live with it. > note: it's untested. Works for me on ppc64 with 4k and 64k pages. Thanks! I'd still like someone with a CONFIG_STACK_GROWSUP arch to test/ACK it as well. Mikey > > > > =============== > From: Michael Neuling <mikey@neuling.org> > Subject: Restrict initial stack space expansion to rlimit > > When reserving stack space for a new process, make sure we're not > attempting to expand the stack by more than rlimit allows. > > This fixes a bug caused by b6a2fea39318e43fee84fa7b0b90d68bed92d2ba "mm: > variable length argument support" and unmasked by > fc63cf237078c86214abcb2ee9926d8ad289da9b "exec: setup_arg_pages() fails > to return errors". This bug means when limiting the stack to less the > 20*PAGE_SIZE (eg. 80K on 4K pages or 'ulimit -s 79') all processes will > be killed before they start. This is particularly bad with 64K pages, > where a ulimit below 1280K will kill every process. > > [kosaki.motohiro@jp.fujitsu.com: cleanups] > Signed-off-by: Michael Neuling <mikey@neuling.org> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > Cc: stable@kernel.org > --- > Attempts to answer comments from Kosaki Motohiro. > > Tested on PPC only, hence !CONFIG_STACK_GROWSUP. Someone should > probably ACK for an arch with CONFIG_STACK_GROWSUP. > > As noted, stable needs the same patch, but 2.6.32 doesn't have the > rlimit() helper. > > diff --git a/fs/exec.c b/fs/exec.c > index 6f7fb0c..325bad4 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -573,6 +573,9 @@ int setup_arg_pages(struct linux_binprm *bprm, > struct vm_area_struct *prev = NULL; > unsigned long vm_flags; > unsigned long stack_base; > + unsigned long stack_size; > + unsigned long stack_expand; > + unsigned long rlim_stack; > > #ifdef CONFIG_STACK_GROWSUP > /* Limit stack size to 1GB */ > @@ -629,10 +632,27 @@ int setup_arg_pages(struct linux_binprm *bprm, > goto out_unlock; > } > > + stack_expand = EXTRA_STACK_VM_PAGES * PAGE_SIZE; > + stack_size = vma->vm_end - vma->vm_start; > + /* > + * Align this down to a page boundary as expand_stack > + * will align it up. > + */ > + rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK; > + if (rlim_stack < stack_size) > + rlim_stack = stack_size; > #ifdef CONFIG_STACK_GROWSUP > - stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE; > + if (stack_size + stack_expand > rlim_stack) { > + stack_base = vma->vm_start + rlim_stack; > + } else { > + stack_base = vma->vm_end + stack_expand; > + } > #else > - stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE; > + if (stack_size + stack_expand > rlim_stack) { > + stack_base = vma->vm_end - rlim_stack; > + } else { > + stack_base = vma->vm_start - stack_expand; > + } > #endif > ret = expand_stack(vma, stack_base); > if (ret) > > >
=============== From: Michael Neuling <mikey@neuling.org> Subject: Restrict initial stack space expansion to rlimit When reserving stack space for a new process, make sure we're not attempting to expand the stack by more than rlimit allows. This fixes a bug caused by b6a2fea39318e43fee84fa7b0b90d68bed92d2ba "mm: variable length argument support" and unmasked by fc63cf237078c86214abcb2ee9926d8ad289da9b "exec: setup_arg_pages() fails to return errors". This bug means when limiting the stack to less the 20*PAGE_SIZE (eg. 80K on 4K pages or 'ulimit -s 79') all processes will be killed before they start. This is particularly bad with 64K pages, where a ulimit below 1280K will kill every process. [kosaki.motohiro@jp.fujitsu.com: cleanups] Signed-off-by: Michael Neuling <mikey@neuling.org> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: stable@kernel.org --- Attempts to answer comments from Kosaki Motohiro. Tested on PPC only, hence !CONFIG_STACK_GROWSUP. Someone should probably ACK for an arch with CONFIG_STACK_GROWSUP. As noted, stable needs the same patch, but 2.6.32 doesn't have the rlimit() helper. diff --git a/fs/exec.c b/fs/exec.c index 6f7fb0c..325bad4 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -573,6 +573,9 @@ int setup_arg_pages(struct linux_binprm *bprm, struct vm_area_struct *prev = NULL; unsigned long vm_flags; unsigned long stack_base; + unsigned long stack_size; + unsigned long stack_expand; + unsigned long rlim_stack; #ifdef CONFIG_STACK_GROWSUP /* Limit stack size to 1GB */ @@ -629,10 +632,27 @@ int setup_arg_pages(struct linux_binprm *bprm, goto out_unlock; } + stack_expand = EXTRA_STACK_VM_PAGES * PAGE_SIZE; + stack_size = vma->vm_end - vma->vm_start; + /* + * Align this down to a page boundary as expand_stack + * will align it up. + */ + rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK; + if (rlim_stack < stack_size) + rlim_stack = stack_size; #ifdef CONFIG_STACK_GROWSUP - stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE; + if (stack_size + stack_expand > rlim_stack) { + stack_base = vma->vm_start + rlim_stack; + } else { + stack_base = vma->vm_end + stack_expand; + } #else - stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE; + if (stack_size + stack_expand > rlim_stack) { + stack_base = vma->vm_end - rlim_stack; + } else { + stack_base = vma->vm_start - stack_expand; + } #endif ret = expand_stack(vma, stack_base); if (ret)