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Message-ID: <15521.1266224231@neuling.org> Date: Mon, 15 Feb 2010 19:57:11 +1100 From: Michael Neuling <mikey@...ling.org> To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> cc: Jouni Malinen <j@...fi>, linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, anton@...ba.org Subject: [PATCH] exec/fs: fix initial stack reservation In message <20100215155821.7298.A69D9226@...fujitsu.com> you wrote: > > > > > > In message <20100214164023.GA2726@...kir.nu> you wrote: > > > It looks like the commit 803bf5ec259941936262d10ecc84511b76a20921 > > > (fs/exec.c: restrict initial stack space expansion to rlimit) broke my > > > user mode Linux setup by somehow preventing system setup from running > > > properly (or killing some processes that try to mount things, etc.). > > > This commit turned up as the reason based on git bisect and reverting it > > > fixes my UML test setup (Ubuntu 9.10 on both host and in UML and AMD64 > > > arch for both). I have no idea what exactly would be the main cause for > > > this issue, but this looks like a somewhat unfortunately timed > > > regression in 2.6.33-rc8. > > > > > > The failed run shows like this (with current linux-2.6.git): > > > > > > ... > > > EXT3-fs (ubda): mounted filesystem with writeback data mode > > > VFS: Mounted root (ext3 filesystem) readonly on device 98:0. > > > IRQ 3/console-write: IRQF_DISABLED is not guaranteed on shared IRQs > > > IRQ 2/console: IRQF_DISABLED is not guaranteed on shared IRQs > > > IRQ 10/winch: IRQF_DISABLED is not guaranteed on shared IRQs > > > IRQ 10/winch: IRQF_DISABLED is not guaranteed on shared IRQs > > > mountall: mount /sys/kernel/debug [218] killed by KILL signal > > > mountall: Filesystem could not be mounted: /sys/kernel/debug > > > mountall: mount /dev [219] killed by KILL signal > > > mountall: Filesystem could not be mounted: /dev > > > mountall: mount /tmp [220] killed by KILL signal > > > mountall: Filesystem could not be mounted: /tmp > > > mountall: mount /var/lock [222] killed by KILL signal > > > mountall: Filesystem could not be mounted: /var/lock > > > ... > > > > > > > > > With 803bf5ec reverted, UML comes up and the output looks like this: > > > > > > ... > > > EXT3-fs (ubda): mounted filesystem with writeback data mode > > > VFS: Mounted root (ext3 filesystem) readonly on device 98:0. > > > IRQ 3/console-write: IRQF_DISABLED is not guaranteed on shared IRQs > > > IRQ 2/console: IRQF_DISABLED is not guaranteed on shared IRQs > > > IRQ 10/winch: IRQF_DISABLED is not guaranteed on shared IRQs > > > IRQ 10/winch: IRQF_DISABLED is not guaranteed on shared IRQs > > > init: procps main process (226) terminated with status 255 > > > fsck from util-linux-ng 2.16 > > > ... > > > > Jouni, > > > > I can reproduce this now. > > > > We got the logic wrong in one of the cleanups and hence we aren't > > actually changing the stack reservation ever, when we intended on > > allocating up to 20 new pages. > > > > The: > > rlim_stack = min(rlim_stack, stack_size); > > always chooses stack_size hence we end up not changing the stack at all. > > This seems to cause fatal problems on UML, but is obviously not what was > > intended for archs as well. > > > > The following works for me on PPC64 64k and 4k pages and UML on x86_64. > > > > Let me know if it fixes it for you also. > > > > Mikey > > > > > > exec/fs: fix initial stack reservation > > > > 803bf5ec259941936262d10ecc84511b76a20921 (fs/exec.c: restrict initial > > stack space expansion to rlimit) attempts to limit the initial stack to > > 20*PAGE_SIZE. Unfortunately, in also attempting ensure the stack is not > > reduced in size, we ended up not changing the stack at all. > > > > This caused a regression in UML resulting in most guest processes to be > > killed. > > > > Signed-off-by: Michael Neuling <mikey@...ling.org> > > cc: <stable@...nel.org> > > > > diff --git a/fs/exec.c b/fs/exec.c > > index e95c692..e0e7b3c 100644 > > --- a/fs/exec.c > > +++ b/fs/exec.c > > @@ -637,15 +637,16 @@ int setup_arg_pages(struct linux_binprm *bprm, > > * will align it up. > > */ > > rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK; > > - rlim_stack = min(rlim_stack, stack_size); > > #ifdef CONFIG_STACK_GROWSUP > > if (stack_size + stack_expand > rlim_stack) > > - stack_base = vma->vm_start + rlim_stack; > > + /* Expand only to rlimit, making sure not to shrink it */ > > + stack_base = vma->vm_start + max(rlim_stack,stack_size); > > else > > stack_base = vma->vm_end + stack_expand; > > #else > > if (stack_size + stack_expand > rlim_stack) > > - stack_base = vma->vm_end - rlim_stack; > > + /* Expand only to rlimit, making sure not to shrink it */ > > + stack_base = vma->vm_end - max(rlim_stack,stack_size); > > else > > stack_base = vma->vm_start - stack_expand; > > #endif > > - rlim_stack = min(rlim_stack, stack_size); > + /* Expand only to rlimit, making sure not to shrink it */ > + rlim_stack = max(rlim_stack, stack_size); > > is better fix? Actually, I think we can just get rid of min() line altogether. expand_stack checks to make sure the stack is getting bigger, otherwise it does nothing. We don't need to bother with this check. The below works for me on UML x86_64 and ppc64 64k and 4k pages. Mikey exec/fs: fix initial stack reservation 803bf5ec259941936262d10ecc84511b76a20921 (fs/exec.c: restrict initial stack space expansion to rlimit) attempts to limit the initial stack to 20*PAGE_SIZE. Unfortunately, in attempting ensure the stack is not reduced in size, we ended up not changing the stack at all. This size reduction check is not necessary as the expand_stack call does this already. This caused a regression in UML resulting in most guest processes being killed. Signed-off-by: Michael Neuling <mikey@...ling.org> cc: <stable@...nel.org> --- fs/exec.c | 1 - 1 file changed, 1 deletion(-) Index: linux-2.6-ozlabs/fs/exec.c =================================================================== --- linux-2.6-ozlabs.orig/fs/exec.c +++ linux-2.6-ozlabs/fs/exec.c @@ -637,7 +637,6 @@ int setup_arg_pages(struct linux_binprm * will align it up. */ rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK; - rlim_stack = min(rlim_stack, stack_size); #ifdef CONFIG_STACK_GROWSUP if (stack_size + stack_expand > rlim_stack) stack_base = vma->vm_start + rlim_stack; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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