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Message-ID: <202511091815.6q5WUuzH-lkp@intel.com>
Date: Sun, 9 Nov 2025 19:05:11 +0800
From: kernel test robot <lkp@...el.com>
To: syzbot <syzbot+04c2672c56fbb9401640@...kaller.appspotmail.com>,
linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev
Subject: Re: Forwarded: [PATCH] fs: fix inode use-after-free in chown_common
delegation retry
Hi syzbot,
kernel test robot noticed the following build warnings:
[auto build test WARNING on brauner-vfs/vfs.all]
[also build test WARNING on linus/master v6.18-rc4 next-20251107]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/syzbot/Forwarded-PATCH-fs-fix-inode-use-after-free-in-chown_common-delegation-retry/20251109-171000
base: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git vfs.all
patch link: https://lore.kernel.org/r/691059ff.a70a0220.22f260.00a6.GAE%40google.com
patch subject: Forwarded: [PATCH] fs: fix inode use-after-free in chown_common delegation retry
config: arm-allnoconfig (https://download.01.org/0day-ci/archive/20251109/202511091815.6q5WUuzH-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project b9ea93cd5c37fb6d606502fd01208dd48330549d)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251109/202511091815.6q5WUuzH-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511091815.6q5WUuzH-lkp@intel.com/
All warnings (new ones prefixed by >>):
>> fs/open.c:771:9: warning: format specifies type 'void *' but the argument has type 'long' [-Wformat]
769 | printk("DEBUG: [%s] retry_deleg: inode=%p, i_count=%d, i_rwsem.owner=%px\n",
| ~~
| %ld
770 | current->comm, inode, atomic_read(&inode->i_count),
771 | atomic_long_read(&inode->i_rwsem.owner));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/printk.h:512:60: note: expanded from macro 'printk'
512 | #define printk(fmt, ...) printk_index_wrap(_printk, fmt, ##__VA_ARGS__)
| ~~~ ^~~~~~~~~~~
include/linux/printk.h:484:19: note: expanded from macro 'printk_index_wrap'
484 | _p_func(_fmt, ##__VA_ARGS__); \
| ~~~~ ^~~~~~~~~~~
fs/open.c:785:31: warning: format specifies type 'void *' but the argument has type 'long' [-Wformat]
784 | printk("DEBUG: [%s] after inode_lock: inode=%p, i_rwsem.owner=%px (current=%px)\n",
| ~~
| %ld
785 | current->comm, inode, atomic_long_read(&inode->i_rwsem.owner), current);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/printk.h:512:60: note: expanded from macro 'printk'
512 | #define printk(fmt, ...) printk_index_wrap(_printk, fmt, ##__VA_ARGS__)
| ~~~ ^~~~~~~~~~~
include/linux/printk.h:484:19: note: expanded from macro 'printk_index_wrap'
484 | _p_func(_fmt, ##__VA_ARGS__); \
| ~~~~ ^~~~~~~~~~~
fs/open.c:798:31: warning: format specifies type 'void *' but the argument has type 'long' [-Wformat]
797 | printk("DEBUG: [%s] before inode_unlock: inode=%p, i_rwsem.owner=%px, delegated_inode=%p\n",
| ~~
| %ld
798 | current->comm, inode, atomic_long_read(&inode->i_rwsem.owner), delegated_inode);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/printk.h:512:60: note: expanded from macro 'printk'
512 | #define printk(fmt, ...) printk_index_wrap(_printk, fmt, ##__VA_ARGS__)
| ~~~ ^~~~~~~~~~~
include/linux/printk.h:484:19: note: expanded from macro 'printk_index_wrap'
484 | _p_func(_fmt, ##__VA_ARGS__); \
| ~~~~ ^~~~~~~~~~~
fs/open.c:801:31: warning: format specifies type 'void *' but the argument has type 'long' [-Wformat]
800 | printk("DEBUG: [%s] after inode_unlock: inode=%p, i_rwsem.owner=%px\n",
| ~~
| %ld
801 | current->comm, inode, atomic_long_read(&inode->i_rwsem.owner));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/printk.h:512:60: note: expanded from macro 'printk'
512 | #define printk(fmt, ...) printk_index_wrap(_printk, fmt, ##__VA_ARGS__)
| ~~~ ^~~~~~~~~~~
include/linux/printk.h:484:19: note: expanded from macro 'printk_index_wrap'
484 | _p_func(_fmt, ##__VA_ARGS__); \
| ~~~~ ^~~~~~~~~~~
4 warnings generated.
vim +771 fs/open.c
750
751 int chown_common(const struct path *path, uid_t user, gid_t group)
752 {
753 struct mnt_idmap *idmap;
754 struct user_namespace *fs_userns;
755 struct inode *inode = path->dentry->d_inode;
756 struct inode *delegated_inode = NULL;
757 int error;
758 struct iattr newattrs;
759 kuid_t uid;
760 kgid_t gid;
761
762 uid = make_kuid(current_user_ns(), user);
763 gid = make_kgid(current_user_ns(), group);
764
765 idmap = mnt_idmap(path->mnt);
766 fs_userns = i_user_ns(inode);
767
768 retry_deleg:
769 printk("DEBUG: [%s] retry_deleg: inode=%p, i_count=%d, i_rwsem.owner=%px\n",
770 current->comm, inode, atomic_read(&inode->i_count),
> 771 atomic_long_read(&inode->i_rwsem.owner));
772 newattrs.ia_vfsuid = INVALID_VFSUID;
773 newattrs.ia_vfsgid = INVALID_VFSGID;
774 newattrs.ia_valid = ATTR_CTIME;
775 if ((user != (uid_t)-1) && !setattr_vfsuid(&newattrs, uid))
776 return -EINVAL;
777 if ((group != (gid_t)-1) && !setattr_vfsgid(&newattrs, gid))
778 return -EINVAL;
779 printk("DEBUG: [%s] before inode_lock: inode=%p, i_count=%d\n",
780 current->comm, inode, atomic_read(&inode->i_count));
781 error = inode_lock_killable(inode);
782 if (error)
783 return error;
784 printk("DEBUG: [%s] after inode_lock: inode=%p, i_rwsem.owner=%px (current=%px)\n",
785 current->comm, inode, atomic_long_read(&inode->i_rwsem.owner), current);
786 if (!S_ISDIR(inode->i_mode))
787 newattrs.ia_valid |= ATTR_KILL_SUID | ATTR_KILL_PRIV |
788 setattr_should_drop_sgid(idmap, inode);
789 /* Continue to send actual fs values, not the mount values. */
790 error = security_path_chown(
791 path,
792 from_vfsuid(idmap, fs_userns, newattrs.ia_vfsuid),
793 from_vfsgid(idmap, fs_userns, newattrs.ia_vfsgid));
794 if (!error)
795 error = notify_change(idmap, path->dentry, &newattrs,
796 &delegated_inode);
797 printk("DEBUG: [%s] before inode_unlock: inode=%p, i_rwsem.owner=%px, delegated_inode=%p\n",
798 current->comm, inode, atomic_long_read(&inode->i_rwsem.owner), delegated_inode);
799 inode_unlock(inode);
800 printk("DEBUG: [%s] after inode_unlock: inode=%p, i_rwsem.owner=%px\n",
801 current->comm, inode, atomic_long_read(&inode->i_rwsem.owner));
802 if (delegated_inode) {
803 printk("DEBUG: [%s] calling break_deleg_wait: inode=%p, i_count=%d, delegated_inode=%p\n",
804 current->comm, inode, atomic_read(&inode->i_count), delegated_inode);
805 error = break_deleg_wait(&delegated_inode);
806 printk("DEBUG: [%s] after break_deleg_wait: inode=%p, i_count=%d, error=%d\n",
807 current->comm, inode, atomic_read(&inode->i_count), error);
808 if (!error)
809 goto retry_deleg;
810 }
811 return error;
812 }
813
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
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