[x86] Drop fix for #865303, which no longer affects Debian's OpenJDK
This workaround is no longer needed for Debian's OpenJDK packages: * OpenJDK 7 is unfixed (bug #876068) but is not present in stretch or later suites * OpenJDK 8 was fixed in unstable (bug #876051) and the fix was then included in a stretch security update * OpenJDK 9 and later were fixed (bug #876069) The workaround was never applied upstream and it also doesn't seem like a good idea to have a Debian-specific VM quirk that weakens the defence against Stack Clash. Therefore drop it now rather than including it in another release.
This commit is contained in:
Ben Hutchings
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7064a34f6e
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20351317dd
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@ -1,6 +1,7 @@
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linux (4.19.28-2) UNRELEASED; urgency=medium
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* [x86,alpha,m68k] binfmt: Disable BINFMT_AOUT, IA32_AOUT, OSF4_COMPAT
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* [x86] Drop fix for #865303, which no longer affects Debian's OpenJDK
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-- Ben Hutchings <ben@decadent.org.uk> Tue, 12 Mar 2019 15:44:31 +0000
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@ -1,45 +0,0 @@
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From: Ben Hutchings <ben@decadent.org.uk>
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Date: Thu, 30 Nov 2017 00:29:18 +0000
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Subject: mmap: Add an exception to the stack gap for Hotspot JVM compatibility
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Bug-Debian: https://bugs.debian.org/865303
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The Hotspot JVM can easily exhaust the default stack, and has a
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SIGSEGV handler to cope with this by switching to a new stack segment.
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However, on i386 it creates a single writable and executable page just
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under the stack limit as a workaround for a bug in Exec Shield. That
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together with the enlarged stack gap causes the SIGSEGV handler to be
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triggered when the stack pointer is further away from the stack limit,
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and it doesn't recognise this as being a stack overflow.
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This specifically affects programs that use JNI. Hotspot doesn't
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normally run Java code on the initial thread.
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Reduce the effective stack guard gap on x86 if the previous vma is
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a single page allocated as MAP_FIXED.
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References: https://bugs.debian.org/865303
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Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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---
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mm/mmap.c | 10 ++++++++++
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1 file changed, 10 insertions(+)
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--- a/mm/mmap.c
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+++ b/mm/mmap.c
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@@ -2328,6 +2328,16 @@ int expand_downwards(struct vm_area_struct *vma,
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/* Check that both stack segments have the same anon_vma? */
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if (prev && !(prev->vm_flags & VM_GROWSDOWN) &&
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(prev->vm_flags & (VM_WRITE|VM_READ|VM_EXEC))) {
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+ /*
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+ * bwh: Reduce the stack guard gap if this looks like
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+ * Hotspot JVM craziness - see Debian bug #865303
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+ */
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+ if (IS_ENABLED(CONFIG_X86) && (prev->vm_flags & VM_FIXED) &&
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+ prev->vm_end - prev->vm_start == PAGE_SIZE) {
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+ if (address - prev->vm_end <
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+ min(stack_guard_gap, 4UL << PAGE_SHIFT))
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+ return -ENOMEM;
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+ } else
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if (address - prev->vm_end < stack_guard_gap)
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return -ENOMEM;
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}
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@ -1,40 +0,0 @@
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From: Ben Hutchings <ben@decadent.org.uk>
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Date: Wed, 5 Jul 2017 13:32:43 +0100
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Subject: mmap: Remember the MAP_FIXED flag as VM_FIXED
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Since 4.15 there are no spare bits, but we can use VM_ARCH_1 as
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VM_FIXED wil only be needed on x86.
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Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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---
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include/linux/mm.h | 1 +
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include/linux/mman.h | 3 ++-
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2 files changed, 3 insertions(+), 1 deletion(-)
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--- a/include/linux/mm.h
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+++ b/include/linux/mm.h
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@@ -201,6 +201,11 @@ extern unsigned int kobjsize(const void
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#define VM_HUGETLB 0x00400000 /* Huge TLB Page VM */
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#define VM_SYNC 0x00800000 /* Synchronous page faults */
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#define VM_ARCH_1 0x01000000 /* Architecture-specific flag */
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+#ifdef CONFIG_X86
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+#define VM_FIXED VM_ARCH_1 /* Allocated at fixed address */
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+#else
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+#define VM_FIXED 0
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+#endif
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#define VM_WIPEONFORK 0x02000000 /* Wipe VMA contents in child. */
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#define VM_DONTDUMP 0x04000000 /* Do not include in the core dump */
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--- a/include/linux/mman.h
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+++ b/include/linux/mman.h
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@@ -131,7 +131,9 @@ calc_vm_flag_bits(unsigned long flags)
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return _calc_vm_trans(flags, MAP_GROWSDOWN, VM_GROWSDOWN ) |
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_calc_vm_trans(flags, MAP_DENYWRITE, VM_DENYWRITE ) |
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_calc_vm_trans(flags, MAP_LOCKED, VM_LOCKED ) |
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- _calc_vm_trans(flags, MAP_SYNC, VM_SYNC );
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+ _calc_vm_trans(flags, MAP_SYNC, VM_SYNC ) |
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+ (VM_FIXED ?
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+ _calc_vm_trans(flags, MAP_FIXED, VM_FIXED ) : 0);
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}
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unsigned long vm_commit_limit(void);
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@ -69,8 +69,6 @@ bugfix/x86/platform-x86-ideapad-laptop-add-ideapad-v510-15ikb-t.patch
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bugfix/x86/platform-x86-ideapad-laptop-add-several-models-to-no.patch
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bugfix/x86/perf-tools-fix-unwind-build-on-i386.patch
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bugfix/sh/sh-boot-do-not-use-hyphen-in-exported-variable-name.patch
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bugfix/x86/mmap-remember-the-map_fixed-flag-as-vm_fixed.patch
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bugfix/x86/mmap-add-an-exception-to-the-stack-gap-for-hotspot-jvm.patch
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bugfix/powerpc/powerpc-lib-sstep-fix-building-for-powerpcspe.patch
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bugfix/powerpc/powerpc-lib-makefile-don-t-pull-in-quad.o-for-32-bit.patch
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bugfix/arm/arm-mm-export-__sync_icache_dcache-for-xen-privcmd.patch
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