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| author | Maxim Kuvyrkov <maxim@kugelworks.com> | 2013-12-24 09:44:50 +1300 |
|---|---|---|
| committer | Maxim Kuvyrkov <maxim@kugelworks.com> | 2014-01-05 15:02:11 +1300 |
| commit | 9875bb22212391e39d9d2c29b4b5d5e9e1f83beb (patch) | |
| tree | 9571693b689aff22ac298bf89c9038e3ced21d48 | |
| parent | 53fa2b6063a484e19a6c48c4efff00a6491c0f4e (diff) | |
| download | glibc-9875bb22212391e39d9d2c29b4b5d5e9e1f83beb.tar.gz glibc-9875bb22212391e39d9d2c29b4b5d5e9e1f83beb.tar.xz glibc-9875bb22212391e39d9d2c29b4b5d5e9e1f83beb.zip | |
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
| -rw-r--r-- | ChangeLog | 7 | ||||
| -rw-r--r-- | NEWS | 2 | ||||
| -rw-r--r-- | malloc/malloc.c | 20 |
3 files changed, 20 insertions, 9 deletions
diff --git a/ChangeLog b/ChangeLog index dd64c05234..92b313878b 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,10 @@ +2014-01-04 Maxim Kuvyrkov <maxim@kugelworks.com> + Ondřej Bílka <neleai@seznam.cz> + + [BZ #15073] + * malloc/malloc.c (_int_free): Perform sanity check only if we + have_lock. + 2012-01-28 Chris Metcalf <cmetcalf@tilera.com> * sysdeps/unix/sysv/linux/faccessat.c (faccessat): Call __fxstatat64. diff --git a/NEWS b/NEWS index 00b447a472..1f631ed8d6 100644 --- a/NEWS +++ b/NEWS @@ -11,7 +11,7 @@ Version 2.15.1 411, 2547, 2548, 11261, 11365, 11494, 13583, 13731, 13732, 13733, 13747, 13748, 13749, 13753, 13754, 13771, 13773, 13774, 13786, 14048, 14059, - 14167, 14273, 14459, 14621, 14648, 14040 + 14167, 14273, 14459, 14621, 14648, 14040, 15073 Version 2.15 diff --git a/malloc/malloc.c b/malloc/malloc.c index 8608083adb..aeda31d27f 100644 --- a/malloc/malloc.c +++ b/malloc/malloc.c @@ -3989,25 +3989,29 @@ _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; |