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GNU C Library master sources branch release/2.16/master updated. glibc-2.16.0-22-gc972bcc
- From: mkuvyrkov at sourceware dot org
- To: glibc-cvs at sourceware dot org
- Date: 5 Jan 2014 02:17:55 -0000
- Subject: GNU C Library master sources branch release/2.16/master updated. glibc-2.16.0-22-gc972bcc
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- Log -----------------------------------------------------------------
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=c972bcc9ebdb5c2601b6b34001c7450e7a0b5ea3
commit c972bcc9ebdb5c2601b6b34001c7450e7a0b5ea3
Author: Maxim Kuvyrkov <maxim@kugelworks.com>
Date: Tue Dec 24 09:44:50 2013 +1300
Fix race in free() of fastbin chunk: BZ #15073
Perform sanity check only if we have_lock. Due to lockless nature of fastbins
we need to be careful derefencing pointers to fastbin entries (chunksize(old)
in this case) in multithreaded environments.
The fix is to add have_lock to the if-condition checks. The rest of the patch
only makes code more readable.
* malloc/malloc.c (_int_free): Perform sanity check only if we
have_lock.
Conflicts:
ChangeLog
NEWS
diff --git a/ChangeLog b/ChangeLog
index 3de21fd..d823b11 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2014-01-04 Maxim Kuvyrkov <maxim@kugelworks.com>
+ OndÅ?ej BÃlka <neleai@seznam.cz>
+
+ [BZ #15073]
+ * malloc/malloc.c (_int_free): Perform sanity check only if we
+ have_lock.
+
2012-11-20 Thomas Schwinge <thomas@codesourcery.com>
* sysdeps/sh/dl-machine.h (ELF_MACHINE_RUNTIME_FIXUP_PARAMS): New
diff --git a/NEWS b/NEWS
index 86c6dfc..2c5fb07 100644
--- a/NEWS
+++ b/NEWS
@@ -9,7 +9,7 @@ Version 2.16.1
* The following bugs are resolved with this release:
- 6530, 14195, 14459, 14476, 14562, 14621, 14648, 14756, 14831
+ 6530, 14195, 14459, 14476, 14562, 14621, 14648, 14756, 14831, 15073
Version 2.16
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 28039b4..0ee5676 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -3868,25 +3868,29 @@ _int_free(mstate av, mchunkptr p, int have_lock)
unsigned int idx = fastbin_index(size);
fb = &fastbin (av, idx);
- mchunkptr fd;
- mchunkptr old = *fb;
+ /* Atomically link P to its fastbin: P->FD = *FB; *FB = P; */
+ mchunkptr old = *fb, old2;
unsigned int old_idx = ~0u;
do
{
- /* Another simple check: make sure the top of the bin is not the
- record we are going to add (i.e., double free). */
+ /* Check that the top of the bin is not the record we are going to add
+ (i.e., double free). */
if (__builtin_expect (old == p, 0))
{
errstr = "double free or corruption (fasttop)";
goto errout;
}
- if (old != NULL)
+ /* Check that size of fastbin chunk at the top is the same as
+ size of the chunk that we are adding. We can dereference OLD
+ only if we have the lock, otherwise it might have already been
+ deallocated. See use of OLD_IDX below for the actual check. */
+ if (have_lock && old != NULL)
old_idx = fastbin_index(chunksize(old));
- p->fd = fd = old;
+ p->fd = old2 = old;
}
- while ((old = catomic_compare_and_exchange_val_rel (fb, p, fd)) != fd);
+ while ((old = catomic_compare_and_exchange_val_rel (fb, p, old2)) != old2);
- if (fd != NULL && __builtin_expect (old_idx != idx, 0))
+ if (have_lock && old != NULL && __builtin_expect (old_idx != idx, 0))
{
errstr = "invalid fastbin entry (free)";
goto errout;
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 7 +++++++
NEWS | 2 +-
malloc/malloc.c | 20 ++++++++++++--------
3 files changed, 20 insertions(+), 9 deletions(-)
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