[kernel/f14/master] Fix fallout from the stack guard page fixes.
Chuck Ebbert
cebbert at fedoraproject.org
Tue Aug 17 22:26:00 UTC 2010
commit bfc8e84a86ee21140cd3882d4ccd49266d1cb0bc
Author: Chuck Ebbert <cebbert at redhat.com>
Date: Tue Aug 17 18:26:23 2010 -0400
Fix fallout from the stack guard page fixes.
(mm-fix-page-table-unmap-for-stack-guard-page-properly.patch,
mm-fix-up-some-user-visible-effects-of-the-stack-guard-page.patch)
kernel.spec | 14 +++-
...table-unmap-for-stack-guard-page-properly.patch | 71 ++++++++++++++++
...r-visible-effects-of-the-stack-guard-page.patch | 85 ++++++++++++++++++++
3 files changed, 169 insertions(+), 1 deletions(-)
---
diff --git a/kernel.spec b/kernel.spec
index b300e45..cd59c08 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -710,6 +710,9 @@ Patch12050: direct-io-move-aio_complete-into-end_io.patch
Patch12060: ext4-move-aio-completion-after-unwritten-extent-conversion.patch
Patch12070: xfs-move-aio-completion-after-unwritten-extent-conversion.patch
+Patch12070: mm-fix-page-table-unmap-for-stack-guard-page-properly.patch
+Patch12071: mm-fix-up-some-user-visible-effects-of-the-stack-guard-page.patch
+
%endif
BuildRoot: %{_tmppath}/kernel-%{KVERREL}-root
@@ -1305,6 +1308,10 @@ ApplyPatch direct-io-move-aio_complete-into-end_io.patch
ApplyPatch ext4-move-aio-completion-after-unwritten-extent-conversion.patch
ApplyPatch xfs-move-aio-completion-after-unwritten-extent-conversion.patch
+# fix fallout from stack guard page patches
+ApplyPatch mm-fix-page-table-unmap-for-stack-guard-page-properly.patch
+ApplyPatch mm-fix-up-some-user-visible-effects-of-the-stack-guard-page.patch
+
# END OF PATCH APPLICATIONS
%endif
@@ -1891,6 +1898,11 @@ fi
# and build.
%changelog
+* Tue Aug 17 2010 Chuck Ebbert <cebbert at redhat.com> 2.6.35.2-9
+- Fix fallout from the stack guard page fixes.
+ (mm-fix-page-table-unmap-for-stack-guard-page-properly.patch,
+ mm-fix-up-some-user-visible-effects-of-the-stack-guard-page.patch)
+
* Tue Aug 17 2010 Kyle McMartin <kyle at redhat.com>
- Move cgroup fs to /sys/fs/cgroup instead of /cgroup in accordance with
upstream change post 2.6.35.
@@ -1901,7 +1913,7 @@ fi
kernel git is modified (obviously not, since it's a tarball.) Fixes make
local.
-* Mon Aug 16 2010 Jarod Wilson <jarod at redhat.com> 2.6.35.2-9
+* Mon Aug 16 2010 Jarod Wilson <jarod at redhat.com>
- Add ir-core streamzap driver, nuke lirc_streamzap
* Sun Aug 15 2010 Chuck Ebbert <cebbert at redhat.com> 2.6.35.2-8
diff --git a/mm-fix-page-table-unmap-for-stack-guard-page-properly.patch b/mm-fix-page-table-unmap-for-stack-guard-page-properly.patch
new file mode 100644
index 0000000..0989fe3
--- /dev/null
+++ b/mm-fix-page-table-unmap-for-stack-guard-page-properly.patch
@@ -0,0 +1,71 @@
+From: Linus Torvalds <torvalds at linux-foundation.org>
+Date: Sat, 14 Aug 2010 18:44:56 +0000 (-0700)
+Subject: mm: fix page table unmap for stack guard page properly
+X-Git-Tag: v2.6.36-rc1~20
+X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=11ac552477e32835cb6970bf0a70c210807f5673
+
+mm: fix page table unmap for stack guard page properly
+
+We do in fact need to unmap the page table _before_ doing the whole
+stack guard page logic, because if it is needed (mainly 32-bit x86 with
+PAE and CONFIG_HIGHPTE, but other architectures may use it too) then it
+will do a kmap_atomic/kunmap_atomic.
+
+And those kmaps will create an atomic region that we cannot do
+allocations in. However, the whole stack expand code will need to do
+anon_vma_prepare() and vma_lock_anon_vma() and they cannot do that in an
+atomic region.
+
+Now, a better model might actually be to do the anon_vma_prepare() when
+_creating_ a VM_GROWSDOWN segment, and not have to worry about any of
+this at page fault time. But in the meantime, this is the
+straightforward fix for the issue.
+
+See https://bugzilla.kernel.org/show_bug.cgi?id=16588 for details.
+
+Reported-by: Wylda <wylda at volny.cz>
+Reported-by: Sedat Dilek <sedat.dilek at gmail.com>
+Reported-by: Mike Pagano <mpagano at gentoo.org>
+Reported-by: François Valenduc <francois.valenduc at tvcablenet.be>
+Tested-by: Ed Tomlinson <edt at aei.ca>
+Cc: Pekka Enberg <penberg at kernel.org>
+Cc: Greg KH <gregkh at suse.de>
+Cc: stable at kernel.org
+Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
+---
+
+diff --git a/mm/memory.c b/mm/memory.c
+index 9b3b73f..b6e5fd2 100644
+--- a/mm/memory.c
++++ b/mm/memory.c
+@@ -2792,24 +2792,23 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
+ spinlock_t *ptl;
+ pte_t entry;
+
+- if (check_stack_guard_page(vma, address) < 0) {
+- pte_unmap(page_table);
++ pte_unmap(page_table);
++
++ /* Check if we need to add a guard page to the stack */
++ if (check_stack_guard_page(vma, address) < 0)
+ return VM_FAULT_SIGBUS;
+- }
+
++ /* Use the zero-page for reads */
+ if (!(flags & FAULT_FLAG_WRITE)) {
+ entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
+ vma->vm_page_prot));
+- ptl = pte_lockptr(mm, pmd);
+- spin_lock(ptl);
++ page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
+ if (!pte_none(*page_table))
+ goto unlock;
+ goto setpte;
+ }
+
+ /* Allocate our own private page. */
+- pte_unmap(page_table);
+-
+ if (unlikely(anon_vma_prepare(vma)))
+ goto oom;
+ page = alloc_zeroed_user_highpage_movable(vma, address);
diff --git a/mm-fix-up-some-user-visible-effects-of-the-stack-guard-page.patch b/mm-fix-up-some-user-visible-effects-of-the-stack-guard-page.patch
new file mode 100644
index 0000000..095a933
--- /dev/null
+++ b/mm-fix-up-some-user-visible-effects-of-the-stack-guard-page.patch
@@ -0,0 +1,85 @@
+From: Linus Torvalds <torvalds at linux-foundation.org>
+Date: Sun, 15 Aug 2010 18:35:52 +0000 (-0700)
+Subject: mm: fix up some user-visible effects of the stack guard page
+X-Git-Tag: v2.6.36-rc1~5
+X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=d7824370e26325c881b665350ce64fb0a4fde24a
+
+mm: fix up some user-visible effects of the stack guard page
+
+This commit makes the stack guard page somewhat less visible to user
+space. It does this by:
+
+ - not showing the guard page in /proc/<pid>/maps
+
+ It looks like lvm-tools will actually read /proc/self/maps to figure
+ out where all its mappings are, and effectively do a specialized
+ "mlockall()" in user space. By not showing the guard page as part of
+ the mapping (by just adding PAGE_SIZE to the start for grows-up
+ pages), lvm-tools ends up not being aware of it.
+
+ - by also teaching the _real_ mlock() functionality not to try to lock
+ the guard page.
+
+ That would just expand the mapping down to create a new guard page,
+ so there really is no point in trying to lock it in place.
+
+It would perhaps be nice to show the guard page specially in
+/proc/<pid>/maps (or at least mark grow-down segments some way), but
+let's not open ourselves up to more breakage by user space from programs
+that depends on the exact deails of the 'maps' file.
+
+Special thanks to Henrique de Moraes Holschuh for diving into lvm-tools
+source code to see what was going on with the whole new warning.
+
+Reported-and-tested-by: François Valenduc <francois.valenduc at tvcablenet.be
+Reported-by: Henrique de Moraes Holschuh <hmh at hmh.eng.br>
+Cc: stable at kernel.org
+Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
+---
+
+diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
+index aea1d3f..439fc1f 100644
+--- a/fs/proc/task_mmu.c
++++ b/fs/proc/task_mmu.c
+@@ -210,6 +210,7 @@ static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
+ int flags = vma->vm_flags;
+ unsigned long ino = 0;
+ unsigned long long pgoff = 0;
++ unsigned long start;
+ dev_t dev = 0;
+ int len;
+
+@@ -220,8 +221,13 @@ static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
+ pgoff = ((loff_t)vma->vm_pgoff) << PAGE_SHIFT;
+ }
+
++ /* We don't show the stack guard page in /proc/maps */
++ start = vma->vm_start;
++ if (vma->vm_flags & VM_GROWSDOWN)
++ start += PAGE_SIZE;
++
+ seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n",
+- vma->vm_start,
++ start,
+ vma->vm_end,
+ flags & VM_READ ? 'r' : '-',
+ flags & VM_WRITE ? 'w' : '-',
+diff --git a/mm/mlock.c b/mm/mlock.c
+index 3f82720..49e5e4c 100644
+--- a/mm/mlock.c
++++ b/mm/mlock.c
+@@ -167,6 +167,14 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma,
+ if (vma->vm_flags & VM_WRITE)
+ gup_flags |= FOLL_WRITE;
+
++ /* We don't try to access the guard page of a stack vma */
++ if (vma->vm_flags & VM_GROWSDOWN) {
++ if (start == vma->vm_start) {
++ start += PAGE_SIZE;
++ nr_pages--;
++ }
++ }
++
+ while (nr_pages > 0) {
+ int i;
+
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