[SCM] Hurd branch, master, updated. v0.9.git20210404-18-gd9f93a3

[Samuel Thibault]

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commit d9f93a335f230fe018747c075734646db70bdb7a
Author: Sergey Bugaev <bugaevc@gmail.com>
Date:   Mon May 24 18:43:40 2021 +0300

    procfs: Fix use-after-free
    
    Fix several issues with reference counting in
    rootdir_make_translated_node ():
    
    * Grab an additional reference while still holding the lock.
    
    * Give the node an additional reference for being pointed to
      by the ops.
    
    * Reference the existing node if we find it on the second try,
      not only if we find it on the first try.
    
    * Dereference, not just clean, the created node if it turns out
      to be unneeded.
    
    Fixes a crash with the following backtrace:
    
     #2  0x010855c8 in __assert_fail_backtrace (
         assertion=0x1051148 "! (r.hard == 1 && r.weak == 0) || !\"refcount 
detected use-after-free!\"",
         file=0x1050cec "../../libshouldbeinlibc/refcount.h", line=170, 
function=0x1051220 <__PRETTY_FUNCTION__.3> "refcounts_ref")
         at ../../libshouldbeinlibc/assert-backtrace.c:64
     #3  0x01050358 in refcounts_ref (result=0x0, ref=0x15009a0) at 
../../libshouldbeinlibc/refcount.h:170
     #4  netfs_nref (np=0x15008f0) at ../../libnetfs/nref.c:26
     #5  0x0804c9f4 in rootdir_make_translated_node (dir_hook=0x10001990, 
entry_hook=0x8055180 <__compound_literal.8>)
         at ../../procfs/rootdir.c:674
     #6  0x0804ace3 in procfs_dir_lookup (hook=0x10001c10, name=0x2857efc 
"mounts", np=0x2855d68) at ../../procfs/procfs_dir.c:88
     #7  0x0804a410 in procfs_lookup (np=0x10001c40, name=0x2857efc "mounts", 
npp=0x2855d68) at ../../procfs/procfs.c:185
     #8  0x0804cae5 in dircat_lookup (hook=0x10001d50, name=0x2857efc "mounts", 
np=0x2855d68) at ../../procfs/dircat.c:76
     #9  0x0804a410 in procfs_lookup (np=0x10001d80, name=0x2857efc "mounts", 
npp=0x2855d68) at ../../procfs/procfs.c:185
     #10 0x0804a96f in netfs_attempt_lookup (user=0x1401c60, dir=0x10001d80, 
name=0x2857efc "mounts", np=0x2855d68)
         at ../../procfs/netfs.c:212
     #11 0x0103fd5b in netfs_S_dir_lookup (dircred=<optimized out>, 
filename=<optimized out>, flags=<optimized out>,
         mode=<optimized out>, do_retry=<optimized out>, retry_name=<optimized 
out>, retry_port=<optimized out>,
         retry_port_type=<optimized out>) at ../../libnetfs/dir-lookup.c:175
    Message-Id: <20210524154340.264885-2-bugaevc@gmail.com>

-----------------------------------------------------------------------

Summary of changes:
 procfs/rootdir.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)


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