[kernel] Fix dentry hash collisions that prevented boot with selinux enabled (rhbz 805371)
Dave Jones
davej at fedoraproject.org
Thu Mar 22 20:54:44 UTC 2012
commit d51e1d2d42cc453e6ead348f83c478d6e75f0a5c
Author: Dave Jones <davej at redhat.com>
Date: Thu Mar 22 16:54:31 2012 -0400
Fix dentry hash collisions that prevented boot with selinux enabled (rhbz 805371)
fix-dentry-hash.patch | 113 +++++++++++++++++++++++++++++++++++++++++++++++++
kernel.spec | 7 +++
2 files changed, 120 insertions(+), 0 deletions(-)
---
diff --git a/fix-dentry-hash.patch b/fix-dentry-hash.patch
new file mode 100644
index 0000000..c5b2f47
--- /dev/null
+++ b/fix-dentry-hash.patch
@@ -0,0 +1,113 @@
+From davej Thu Mar 22 16:38:38 2012
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+Date: Thu, 22 Mar 2012 20:36:58 +0000
+From: Al Viro <viro at ZenIV.linux.org.uk>
+To: Linus Torvalds <torvalds at linux-foundation.org>
+Cc: linux-kernel at vger.kernel.org, xen-devel at lists.xensource.com,
+ Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
+Subject: Re: Regression introduced by
+ bfcfaa77bdf0f775263e906015982a608df01c76 (vfs: use 'unsigned long' accesses
+ for dcache name comparison and hashing)
+Message-ID: <20120322203658.GC6589 at ZenIV.linux.org.uk>
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+
+On Thu, Mar 22, 2012 at 08:24:45PM +0000, Al Viro wrote:
+>
+> OK, full_name_hash()/hash_name() definitely have a mismatch and it's on the
+> names of length 8*n: trivial experiment shows that we have
+> name hash_name full_name_hash
+> a 61 61
+> ab 6261 6261
+> abc 636261 636261
+> abcd 64636261 64636261
+> abcdabc 64c6c4c2 64c6c4c2
+> abcdabcd efcead5 c8c6c4c2
+> abcdabcd9 efceb0e efceb0e
+>
+> Linus, which way do you prefer to shift it? Should hash_name() change to
+> match full_name_hash() or should it be the other way round?
+>
+> What happens is that you get multiplication by 9 and adding 0 in the former,
+> after having added the last full word. In the latter we add the last full
+> word, see that there's nothing left and bugger off.
+
+Guys, could you check if this fixes it?
+
+diff --git a/fs/namei.c b/fs/namei.c
+index 13e6a1f..7451d6f8 100644
+--- a/fs/namei.c
++++ b/fs/namei.c
+@@ -1439,10 +1439,10 @@ unsigned int full_name_hash(const unsigned char *name, unsigned int len)
+
+ for (;;) {
+ a = *(unsigned long *)name;
+- hash *= 9;
+ if (len < sizeof(unsigned long))
+ break;
+ hash += a;
++ hash *= 9;
+ name += sizeof(unsigned long);
+ len -= sizeof(unsigned long);
+ if (!len)
+--
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+
diff --git a/kernel.spec b/kernel.spec
index f4fea4b..5abf407 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -766,6 +766,8 @@ Patch21400: unhandled-irqs-switch-to-polling.patch
Patch22000: weird-root-dentry-name-debug.patch
+Patch23000: fix-dentry-hash.patch
+
%endif
BuildRoot: %{_tmppath}/kernel-%{KVERREL}-root
@@ -1473,6 +1475,8 @@ ApplyPatch unhandled-irqs-switch-to-polling.patch
ApplyPatch weird-root-dentry-name-debug.patch
+ApplyPatch fix-dentry-hash.patch
+
#rhbz 803809 CVE-2012-1179
ApplyPatch mm-thp-fix-pmd_bad-triggering.patch
@@ -2332,6 +2336,9 @@ fi
# ||----w |
# || ||
%changelog
+* Thu Mar 22 2012 Dave Jones <davej at redhat.com>
+- Fix dentry hash collisions that prevented boot with selinux enabled (rhbz 805371)
+
* Thu Mar 22 2012 Dave Jones <davej at redhat.com> 3.4.0-0.rc0.git1.1
- Linux v3.3-4074-g5375871
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