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Avoid confusing compiler with dynamically impossible statically invalid dereference in _dl_close_worker.

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This commit is contained in:
Roland McGrath 2015-04-17 14:29:40 -07:00
parent 328c44c367
commit 2bd2cad9e8
2 changed files with 18 additions and 3 deletions
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5
ChangeLog
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@ -1,5 +1,10 @@
2015-04-17 Roland McGrath <roland@hack.frob.com>
* elf/dl-close.c (_dl_close_worker) [DL_NNS == 1]: Just assert that
IMAP->l_prev cannot be null, and #if out the code for the contrary
case, avoiding 'assert (nsid != LM_ID_BASE)' making the compiler
believe that NS (&_dl_ns[NSID]) could point outside the array.
* elf/dl-open.c (_dl_open): Use __glibc_unlikely in invalid namespace
check. Reject NSID < 0 and NSID >= dl_nns, and check for DL_NNS==1,
before using NSID as an index.

16
elf/dl-close.c
View File

@ -641,9 +641,16 @@ _dl_close_worker (struct link_map *map)
DL_UNMAP (imap);
/* Finally, unlink the data structure and free it. */
if (imap->l_prev != NULL)
imap->l_prev->l_next = imap->l_next;
else
#if DL_NNS == 1
/* The assert in the (imap->l_prev == NULL) case gives
the compiler license to warn that NS points outside
the dl_ns array bounds in that case (as nsid != LM_ID_BASE
is tantamount to nsid >= DL_NNS). That should be impossible
in this configuration, so just assert about it instead. */
assert (nsid == LM_ID_BASE);
assert (imap->l_prev != NULL);
#else
if (imap->l_prev == NULL)
{
assert (nsid != LM_ID_BASE);
ns->_ns_loaded = imap->l_next;
@ -652,6 +659,9 @@ _dl_close_worker (struct link_map *map)
we leave for debuggers to examine. */
r->r_map = (void *) ns->_ns_loaded;
}
else
#endif
imap->l_prev->l_next = imap->l_next;
--ns->_ns_nloaded;
if (imap->l_next != NULL)