linux-stable.git/fs/proc, branch v6.6.145

proc: protect ptrace_may_access() with exec_update_lock (part 1)

2026-07-24T14:03:50+00:00

[ Upstream commit 6650527444dadc63d84aa939d14ecba4fadb2f69 ]

Fix the easy cases where procfs currently calls ptrace_may_access() without
exec_update_lock protection, where the fix is to simply add the extra lock
or use mm_access():

 - do_task_stat(): grab exec_update_lock
 - proc_pid_wchan(): grab exec_update_lock
 - proc_map_files_lookup(): use mm_access() instead of get_task_mm()
 - proc_map_files_readdir(): use mm_access() instead of get_task_mm()
 - proc_ns_get_link(): grab exec_update_lock
 - proc_ns_readlink(): grab exec_update_lock

Fixes: f83ce3e6b02d ("proc: avoid information leaks to non-privileged processes")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn 
Link: https://patch.msgid.link/20260518-procfs-lockfix-part1-v1-1-5c3d20e0ac33@google.com
Signed-off-by: Christian Brauner (Amutable) 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

seqlock: Change do_task_stat() to use scoped_seqlock_read()

2026-07-24T14:03:50+00:00

[ Upstream commit b76f72bea2c601afec81829ea427fc0d20f83216 ]

To simplify the code and make it more readable.

[peterz: change to new interface]
Signed-off-by: Oleg Nesterov 
Signed-off-by: Peter Zijlstra (Intel) 
Stable-dep-of: 6650527444da ("proc: protect ptrace_may_access() with exec_update_lock (part 1)")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

proc: protect ptrace_may_access() with exec_update_lock (FD links)

2026-07-24T14:03:49+00:00

[ Upstream commit 6255da28d4bb5349fe18e84cb043ccd394eba75d ]

proc_pid_get_link() and proc_pid_readlink() currently look up the task from
the pid once, then do the ptrace access check on that task, then look up
the task from the pid a second time to do the actual access.
That's racy in several ways.

To fix it, pass the task to the ->proc_get_link() handler, and instead of
proc_fd_access_allowed(), introduce a new helper call_proc_get_link() that
looks up and locks the task, does the access check, and calls
->proc_get_link().

Fixes: 778c1144771f ("[PATCH] proc: Use sane permission checks on the /proc//fd/ symlinks")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn 
Link: https://patch.msgid.link/20260518-procfs-lockfix-part1-v1-2-5c3d20e0ac33@google.com
Signed-off-by: Christian Brauner (Amutable) 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

proc: rename proc_setattr to proc_nochmod_setattr

2026-07-24T14:03:49+00:00

[ Upstream commit 690005b0b1e6b567c88b7790e6d90d4d6c9e09cc ]

What is currently proc_setattr is a special version added after the more
general procfs ->seattr in commit 6d76fa58b050 ("Don't allow chmod() on
the /proc// files").  Give it a name that reflects that to free the
proc_setattr name and better describe what is doing.

Signed-off-by: Christoph Hellwig 
Link: https://patch.msgid.link/20260325063711.3298685-5-hch@lst.de
Reviewed-by: Jan Kara 
Signed-off-by: Christian Brauner 
Stable-dep-of: 6255da28d4bb ("proc: protect ptrace_may_access() with exec_update_lock (FD links)")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

proc: only bump parent nlink when registering directories

2026-07-24T14:03:36+00:00

commit 16b02eb4b9b272c221255c20d34ccd5db53a3ed3 upstream.

proc_register() increments the parent directory's link count for every
entry it registers, while remove_proc_entry() and remove_proc_subtree()
decrement it only when the removed entry is a directory.  Regular files
thus inflate the parent's count while they exist, and leak one link
permanently on every create and remove cycle.

For example, /proc/bus/pci/00 with twenty-two device files and no
subdirectories reports nlink 24 instead of 2, and SR-IOV VF enable
and disable cycles, each creating and removing the VF config space
entries under /proc/bus/pci/, inflate the link count of that
directory without bound.

Before commit e06689bf5701 ("proc: change ->nlink under
proc_subdir_lock"), the increment lived in proc_mkdir_data() and
proc_create_mount_point(), and was therefore applied only to
directories.  Moving it into proc_register() to bring it under
proc_subdir_lock dropped the S_ISDIR check.

Thus, move the nlink accounting into pde_subdir_insert() and
pde_erase(), only updating it for directories in both, so the link
count is always changed together with the directory entry itself.

Fixes: e06689bf5701 ("proc: change ->nlink under proc_subdir_lock")
Cc: stable@vger.kernel.org # v5.5+
Signed-off-by: Krzysztof Wilczyński 
Link: https://patch.msgid.link/20260613211005.921692-1-kwilczynski@kernel.org
Signed-off-by: Christian Brauner (Amutable) 
Signed-off-by: Greg Kroah-Hartman

procfs: fix missing RCU protection when reading real_parent in do_task_stat()

2026-03-04T12:19:52+00:00

[ Upstream commit 76149d53502cf17ef3ae454ff384551236fba867 ]

When reading /proc/[pid]/stat, do_task_stat() accesses task->real_parent
without proper RCU protection, which leads to:

  cpu 0                               cpu 1
  -----                               -----
  do_task_stat
    var = task->real_parent
                                      release_task
                                        call_rcu(delayed_put_task_struct)
    task_tgid_nr_ns(var)
      rcu_read_lock   <--- Too late to protect task->real_parent!
      task_pid_ptr    <--- UAF!
      rcu_read_unlock

This patch uses task_ppid_nr_ns() instead of task_tgid_nr_ns() to add
proper RCU protection for accessing task->real_parent.

Link: https://lkml.kernel.org/r/20260128083007.3173016-1-alexjlzheng@tencent.com
Fixes: 06fffb1267c9 ("do_task_stat: don't take rcu_read_lock()")
Signed-off-by: Jinliang Zheng 
Acked-by: Oleg Nesterov 
Cc: David Hildenbrand 
Cc: Ingo Molnar 
Cc: Lorenzo Stoakes 
Cc: Mateusz Guzik 
Cc: ruippan 
Cc: Usama Arif 
Signed-off-by: Andrew Morton 
Signed-off-by: Sasha Levin

fs/proc: fix uaf in proc_readdir_de()

2025-11-24T09:30:07+00:00

commit 895b4c0c79b092d732544011c3cecaf7322c36a1 upstream.

Pde is erased from subdir rbtree through rb_erase(), but not set the node
to EMPTY, which may result in uaf access.  We should use RB_CLEAR_NODE()
set the erased node to EMPTY, then pde_subdir_next() will return NULL to
avoid uaf access.

We found an uaf issue while using stress-ng testing, need to run testcase
getdent and tun in the same time.  The steps of the issue is as follows:

1) use getdent to traverse dir /proc/pid/net/dev_snmp6/, and current
   pde is tun3;

2) in the [time windows] unregister netdevice tun3 and tun2, and erase
   them from rbtree.  erase tun3 first, and then erase tun2.  the
   pde(tun2) will be released to slab;

3) continue to getdent process, then pde_subdir_next() will return
   pde(tun2) which is released, it will case uaf access.

CPU 0                                      |    CPU 1
-------------------------------------------------------------------------
traverse dir /proc/pid/net/dev_snmp6/      |   unregister_netdevice(tun->dev)   //tun3 tun2
sys_getdents64()                           |
  iterate_dir()                            |
    proc_readdir()                         |
      proc_readdir_de()                    |     snmp6_unregister_dev()
        pde_get(de);                       |       proc_remove()
        read_unlock(&proc_subdir_lock);    |         remove_proc_subtree()
                                           |           write_lock(&proc_subdir_lock);
        [time window]                      |           rb_erase(&root->subdir_node, &parent->subdir);
                                           |           write_unlock(&proc_subdir_lock);
        read_lock(&proc_subdir_lock);      |
        next = pde_subdir_next(de);        |
        pde_put(de);                       |
        de = next;    //UAF                |

rbtree of dev_snmp6
                        |
                    pde(tun3)
                     /    \
                  NULL  pde(tun2)

Link: https://lkml.kernel.org/r/20251025024233.158363-1-albin_yang@163.com
Signed-off-by: Wei Yang 
Cc: Al Viro 
Cc: Christian Brauner 
Cc: wangzijie 
Cc: Alexey Dobriyan 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

proc: fix type confusion in pde_set_flags()

2025-09-19T14:32:02+00:00

[ Upstream commit 0ce9398aa0830f15f92bbed73853f9861c3e74ff ]

Commit 2ce3d282bd50 ("proc: fix missing pde_set_flags() for net proc
files") missed a key part in the definition of proc_dir_entry:

union {
	const struct proc_ops *proc_ops;
	const struct file_operations *proc_dir_ops;
};

So dereference of ->proc_ops assumes it is a proc_ops structure results in
type confusion and make NULL check for 'proc_ops' not work for proc dir.

Add !S_ISDIR(dp->mode) test before calling pde_set_flags() to fix it.

Link: https://lkml.kernel.org/r/20250904135715.3972782-1-wangzijie1@honor.com
Fixes: 2ce3d282bd50 ("proc: fix missing pde_set_flags() for net proc files")
Signed-off-by: wangzijie 
Reported-by: Brad Spengler 
Closes: https://lore.kernel.org/all/20250903065758.3678537-1-wangzijie1@honor.com/
Cc: Alexey Dobriyan 
Cc: Al Viro 
Cc: Christian Brauner 
Cc: Jiri Slaby 
Cc: Stefano Brivio 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Sasha Levin

proc: fix missing pde_set_flags() for net proc files

2025-09-09T16:56:26+00:00

commit 2ce3d282bd5050fca8577defeff08ada0d55d062 upstream.

To avoid potential UAF issues during module removal races, we use
pde_set_flags() to save proc_ops flags in PDE itself before
proc_register(), and then use pde_has_proc_*() helpers instead of directly
dereferencing pde->proc_ops->*.

However, the pde_set_flags() call was missing when creating net related
proc files.  This omission caused incorrect behavior which FMODE_LSEEK was
being cleared inappropriately in proc_reg_open() for net proc files.  Lars
reported it in this link[1].

Fix this by ensuring pde_set_flags() is called when register proc entry,
and add NULL check for proc_ops in pde_set_flags().

[wangzijie1@honor.com: stash pde->proc_ops in a local const variable, per Christian]
  Link: https://lkml.kernel.org/r/20250821105806.1453833-1-wangzijie1@honor.com
Link: https://lkml.kernel.org/r/20250818123102.959595-1-wangzijie1@honor.com
Link: https://lore.kernel.org/all/20250815195616.64497967@chagall.paradoxon.rec/ [1]
Fixes: ff7ec8dc1b64 ("proc: use the same treatment to check proc_lseek as ones for proc_read_iter et.al")
Signed-off-by: wangzijie 
Reported-by: Lars Wendler 
Tested-by: Stefano Brivio 
Tested-by: Petr Vaněk 
Tested by: Lars Wendler 
Cc: Alexei Starovoitov 
Cc: Alexey Dobriyan 
Cc: Al Viro 
Cc: "Edgecombe, Rick P" 
Cc: Greg Kroah-Hartman 
Cc: Jiri Slaby 
Cc: Kirill A. Shutemov 
Cc: wangzijie 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

proc: use the same treatment to check proc_lseek as ones for proc_read_iter et.al

2025-08-15T10:08:54+00:00

[ Upstream commit ff7ec8dc1b646296f8d94c39339e8d3833d16c05 ]

Check pde->proc_ops->proc_lseek directly may cause UAF in rmmod scenario.
It's a gap in proc_reg_open() after commit 654b33ada4ab("proc: fix UAF in
proc_get_inode()").  Followed by AI Viro's suggestion, fix it in same
manner.

Link: https://lkml.kernel.org/r/20250607021353.1127963-1-wangzijie1@honor.com
Fixes: 3f61631d47f1 ("take care to handle NULL ->proc_lseek()")
Signed-off-by: wangzijie 
Reviewed-by: Alexey Dobriyan 
Cc: Alexei Starovoitov 
Cc: Al Viro 
Cc: "Edgecombe, Rick P" 
Cc: Kirill A. Shuemov 
Signed-off-by: Andrew Morton 
Signed-off-by: Sasha Levin