From 548e9b916f86c06e2cdb50d8f49633f9bec66c7e Mon Sep 17 00:00:00 2001

From: Logan Gunthorpe <logang@deltatee.com>

Date: Wed, 22 Jun 2022 14:25:09 -0600

Subject: [PATCH 34/83] mdadm/Grow: Fix use after close bug by closing after

 fork

The test 07reshape-grow fails most of the time. But it succeeds around

1 in 5 times. When it does succeed, it causes the tests to die because

mdadm has segfaulted.

The segfault was caused by mdadm attempting to repoen a file

descriptor that was already closed. The backtrace of the segfault

was:

  #0  __strncmp_avx2 () at ../sysdeps/x86_64/multiarch/strcmp-avx2.S:101

  #1  0x000056146e31d44b in devnm2devid (devnm=0x0) at util.c:956

  #2  0x000056146e31dab4 in open_dev_flags (devnm=0x0, flags=0)

                         at util.c:1072

  #3  0x000056146e31db22 in open_dev (devnm=0x0) at util.c:1079

  #4  0x000056146e3202e8 in reopen_mddev (mdfd=4) at util.c:2244

  #5  0x000056146e329f36 in start_array (mdfd=4,

              mddev=0x7ffc55342450 "/dev/md0", content=0x7ffc55342860,

              st=0x56146fc78660, ident=0x7ffc55342f70, best=0x56146fc6f5d0,

              bestcnt=10, chosen_drive=0, devices=0x56146fc706b0, okcnt=5,

	      sparecnt=0,  rebuilding_cnt=0, journalcnt=0, c=0x7ffc55342e90,

	      clean=1,  avail=0x56146fc78720 "\001\001\001\001\001",

	      start_partial_ok=0, err_ok=0, was_forced=0)

	                  at Assemble.c:1206

  #6  0x000056146e32c36e in Assemble (st=0x56146fc78660,

               mddev=0x7ffc55342450 "/dev/md0", ident=0x7ffc55342f70,

	       devlist=0x56146fc6e2d0, c=0x7ffc55342e90)

	                 at Assemble.c:1914

  #7  0x000056146e312ac9 in main (argc=11, argv=0x7ffc55343238)

                         at mdadm.c:1510

The file descriptor was closed early in Grow_continue(). The noted commit

moved the close() call to close the fd above the fork which caused the

parent process to return with a closed fd.

This meant reshape_array() and Grow_continue() would return in the parent

with the fd forked. The fd would eventually be passed to reopen_mddev()

which returned an unhandled NULL from fd2devnm() which would then be

dereferenced in devnm2devid.

Fix this by moving the close() call below the fork. This appears to

fix the 07revert-grow test. While we're at it, switch to using

close_fd() to invalidate the file descriptor.

Fixes: 77b72fa82813 ("mdadm/Grow: prevent md's fd from being occupied during delayed time")

Cc: Alex Wu <alexwu@synology.com>

Cc: BingJing Chang <bingjingc@synology.com>

Cc: Danny Shih <dannyshih@synology.com>

Cc: ChangSyun Peng <allenpeng@synology.com>

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>

Acked-by: Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>

Signed-off-by: Jes Sorensen <jes@trained-monkey.org>

---

 Grow.c | 4 +++-

 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Grow.c b/Grow.c

index 8c520d42..97f22c75 100644

--- a/Grow.c

+++ b/Grow.c

@@ -3514,7 +3514,6 @@ started:

 			return 0;

 		}

-	close(fd);

 	/* Now we just need to kick off the reshape and watch, while

 	 * handling backups of the data...

 	 * This is all done by a forked background process.

@@ -3535,6 +3534,9 @@ started:

 		break;

 	}

+	/* Close unused file descriptor in the forked process */

+	close_fd(&fd;;

+

 	/* If another array on the same devices is busy, the

 	 * reshape will wait for them.  This would mean that

 	 * the first section that we suspend will stay suspended

-- 

2.38.1