Fix nscd readlink argument aliasing (bug 22446).

Current GCC mainline detects that nscd calls readlink with the same
buffer for both input and output, which is not valid (those arguments
are both restrict-qualified in POSIX).  This patch makes it use a
separate buffer for readlink's input (with a size that is sufficient
to avoid truncation, so there should be no problems with warnings
about possible truncation, though not strictly minimal, but much
smaller than the buffer for output) to avoid this problem.

Tested compilation for aarch64-linux-gnu with build-many-glibcs.py.

	[BZ #22446]
	* nscd/connections.c (handle_request) [SO_PEERCRED]: Use separate
	buffers for readlink input and output.

(cherry picked from commit 49b036bce9f021ae994a85aee8b410d20b29c8b7)

diff --git a/ChangeLog b/ChangeLog
index 49bcd10abc0c5bf7a1b5e5561bc74210acd9851d..0b7a920673559e506161f4c12220969cd1d3355d 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2017-12-18  Joseph Myers  <joseph@codesourcery.com>
+
+       [BZ #22446]
+       * nscd/connections.c (handle_request) [SO_PEERCRED]: Use separate
+       buffers for readlink input and output.
+
 2017-12-15  Steve Ellcey  <sellcey@cavium.com>
 
        * nscd/dbg_log.c (dbg_log): Increase msg buffer size.

diff --git a/NEWS b/NEWS
index fecdbdf103e32c2ec36c68f9f255dd1aec2b6886..f6c9a1412ccd8192dbe2a141fe815089f2f1ee1a 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -127,6 +127,7 @@ The following bugs are resolved with this release:
   [22375] malloc returns pointer from tcache instead of NULL (CVE-2017-17426)
   [22377] Provide a C++ version of iseqsig
   [22442] if_nametoindex: Check length of ifname before copying it
+  [22446] Fix nscd readlink argument aliasing
   [22447] Avoid use of strlen in getlogin_r
   [22463] Fix p_secstodate overflow handling
   [22627] $ORIGIN in $LD_LIBRARY_PATH is substituted twice

diff --git a/nscd/connections.c b/nscd/connections.c
index cc1ed72077640a8b45b8d70f3abc13814a0e8faf..dab722dcb2f689b44e73836f508277b36ff034ae 100644 (file)
--- a/nscd/connections.c
+++ b/nscd/connections.c
@@ -1077,14 +1077,15 @@ cannot handle old request version %d; current version is %d"),
       if (debug_level > 0)
        {
 #ifdef SO_PEERCRED
+         char pbuf[sizeof ("/proc//exe") + 3 * sizeof (long int)];
 # ifdef PATH_MAX
          char buf[PATH_MAX];
 # else
          char buf[4096];
 # endif
 
-         snprintf (buf, sizeof (buf), "/proc/%ld/exe", (long int) pid);
-         ssize_t n = readlink (buf, buf, sizeof (buf) - 1);
+         snprintf (pbuf, sizeof (pbuf), "/proc/%ld/exe", (long int) pid);
+         ssize_t n = readlink (pbuf, buf, sizeof (buf) - 1);
 
          if (n <= 0)
            dbg_log (_("\