On Mon, 2022-11-07 at 20:03 +0800, Xiubo Li wrote: > On 07/11/2022 18:33, Jeff Layton wrote: > > On Mon, 2022-11-07 at 17:52 +0800, xiubli@xxxxxxxxxx wrote: > > > From: Xiubo Li <xiubli@xxxxxxxxxx> > > > > > > When closing the file descripters in parallel in multiple threads, > > > who are sharing the same file descripters, the filp_close() will > > > remove all the Posix-style locks. But if two threads both calling > > > the filp_close() it may race and cause use-after-free crash: > > > > > > PID: 327771 TASK: ffff952aa1db3180 CPU: 8 COMMAND: "db2fmp" > > > #0 [ffff95202f33b960] machine_kexec at ffffffff890662f4 > > > #1 [ffff95202f33b9c0] __crash_kexec at ffffffff89122b82 > > > #2 [ffff95202f33ba90] crash_kexec at ffffffff89122c70 > > > #3 [ffff95202f33baa8] oops_end at ffffffff89791798 > > > #4 [ffff95202f33bad0] no_context at ffffffff89075d14 > > > #5 [ffff95202f33bb20] __bad_area_nosemaphore at ffffffff89075fe2 > > > #6 [ffff95202f33bb70] bad_area_nosemaphore at ffffffff89076104 > > > #7 [ffff95202f33bb80] __do_page_fault at ffffffff89794750 > > > #8 [ffff95202f33bbf0] do_page_fault at ffffffff89794975 > > > #9 [ffff95202f33bc20] page_fault at ffffffff89790778 > > > [exception RIP: ceph_fl_release_lock+20] > > > RIP: ffffffffc08247a4 RSP: ffff95202f33bcd0 RFLAGS: 00010286 > > > RAX: ffff952d4ebd8a00 RBX: 0000000000000000 RCX: dead000000000200 > > > RDX: ffff95202f33bd60 RSI: ffff95202f33bd60 RDI: ffff9526b6ac5b00 > > > RBP: ffff95202f33bce0 R8: ffff9526b6ac5b18 R9: ffffffffc083c368 > > > R10: 0000000000001109 R11: 0000000000000000 R12: ffff95202f33bd60 > > > R13: ffff9526b6ac5b00 R14: 0000000000000000 R15: 0000000000000000 > > > ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 > > > #10 [ffff95202f33bce8] locks_release_private at ffffffff892ab3d7 > > > #11 [ffff95202f33bd00] locks_free_lock at ffffffff892ac34d > > > #12 [ffff95202f33bd18] locks_dispose_list at ffffffff892ac44b > > > #13 [ffff95202f33bd40] __posix_lock_file at ffffffff892acdfa > > > #14 [ffff95202f33bda8] posix_lock_file at ffffffff892ad146 > > > #15 [ffff95202f33bdb8] ceph_lock at ffffffffc0824e8a [ceph] > > > #16 [ffff95202f33bdf8] vfs_lock_file at ffffffff892ad185 > > > #17 [ffff95202f33be08] locks_remove_posix at ffffffff892ad239 > > > #18 [ffff95202f33bee0] locks_remove_posix at ffffffff892ad2a0 > > > #19 [ffff95202f33bef0] filp_close at ffffffff8924baa6 > > > #20 [ffff95202f33bf18] __close_fd at ffffffff8926f89c > > > #21 [ffff95202f33bf40] sys_close at ffffffff8924d503 > > > #22 [ffff95202f33bf50] system_call_fastpath at ffffffff89799f92 > > > RIP: 00007f806ec446ab RSP: 00007f80517f0d90 RFLAGS: 00010206 > > > RAX: 0000000000000003 RBX: 00007f8030001a20 RCX: 00007f80300386b0 > > > RDX: 00007f806ef0d880 RSI: 0000000000000001 RDI: 0000000000000006 > > > RBP: 00007f806ef0e3c0 R8: 00007f80517fa700 R9: 0000000000000000 > > > R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000 > > > R13: 00007f80300035b0 R14: 00007f80517f1104 R15: 000000000000006c > > > ORIG_RAX: 0000000000000003 CS: 0033 SS: 002b > > > > > > We need to make sure that the filp in the file_lock shouldn't be > > > release when any file_lock is still referring to it. > > > > > > For the Posix-style locks, whose owner will be the thread ids, we > > > will increase the filp's reference. > > > > > > URL: https://tracker.ceph.com/issues/57986 > > > Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx> > > > --- > > > drivers/android/binder.c | 2 +- > > > fs/file.c | 15 ++++++++++----- > > > fs/locks.c | 18 +++++++++++++++--- > > > include/linux/fs.h | 14 ++++++++++++++ > > > io_uring/openclose.c | 3 ++- > > > 5 files changed, 42 insertions(+), 10 deletions(-) > > > > > > diff --git a/drivers/android/binder.c b/drivers/android/binder.c > > > index 880224ec6abb..03692564d940 100644 > > > --- a/drivers/android/binder.c > > > +++ b/drivers/android/binder.c > > > @@ -1924,7 +1924,7 @@ static void binder_deferred_fd_close(int fd) > > > if (twcb->file) { > > > // pin it until binder_do_fd_close(); see comments there > > > get_file(twcb->file); > > > - filp_close(twcb->file, current->files); > > > + filp_close(twcb->file, file_lock_make_thread_owner(current->files)); > > > task_work_add(current, &twcb->twork, TWA_RESUME); > > > } else { > > > kfree(twcb); > > > diff --git a/fs/file.c b/fs/file.c > > > index 5f9c802a5d8d..39ad8e74a8d9 100644 > > > --- a/fs/file.c > > > +++ b/fs/file.c > > > @@ -417,6 +417,7 @@ static struct fdtable *close_files(struct files_struct * files) > > > * files structure. > > > */ > > > struct fdtable *fdt = rcu_dereference_raw(files->fdt); > > > + fl_owner_t owner = file_lock_make_thread_owner(files); > > > unsigned int i, j = 0; > > > > > > for (;;) { > > > @@ -429,7 +430,7 @@ static struct fdtable *close_files(struct files_struct * files) > > > if (set & 1) { > > > struct file * file = xchg(&fdt->fd[i], NULL); > > > if (file) { > > > - filp_close(file, files); > > > + filp_close(file, owner); > > > cond_resched(); > > > } > > > } > > > @@ -653,6 +654,7 @@ static struct file *pick_file(struct files_struct *files, unsigned fd) > > > int close_fd(unsigned fd) > > > { > > > struct files_struct *files = current->files; > > > + fl_owner_t owner = file_lock_make_thread_owner(files); > > > struct file *file; > > > > > > spin_lock(&files->file_lock); > > > @@ -661,7 +663,7 @@ int close_fd(unsigned fd) > > > if (!file) > > > return -EBADF; > > > > > > - return filp_close(file, files); > > > + return filp_close(file, owner); > > > } > > > EXPORT_SYMBOL(close_fd); /* for ksys_close() */ > > > > > > @@ -695,6 +697,7 @@ static inline void __range_cloexec(struct files_struct *cur_fds, > > > static inline void __range_close(struct files_struct *cur_fds, unsigned int fd, > > > unsigned int max_fd) > > > { > > > + fl_owner_t owner = file_lock_make_thread_owner(cur_fds); > > > unsigned n; > > > > > > rcu_read_lock(); > > > @@ -711,7 +714,7 @@ static inline void __range_close(struct files_struct *cur_fds, unsigned int fd, > > > > > > if (file) { > > > /* found a valid file to close */ > > > - filp_close(file, cur_fds); > > > + filp_close(file, owner); > > > cond_resched(); > > > } > > > } > > > @@ -816,6 +819,7 @@ struct file *close_fd_get_file(unsigned int fd) > > > > > > void do_close_on_exec(struct files_struct *files) > > > { > > > + fl_owner_t owner = file_lock_make_thread_owner(files); > > > unsigned i; > > > struct fdtable *fdt; > > > > > > @@ -841,7 +845,7 @@ void do_close_on_exec(struct files_struct *files) > > > rcu_assign_pointer(fdt->fd[fd], NULL); > > > __put_unused_fd(files, fd); > > > spin_unlock(&files->file_lock); > > > - filp_close(file, files); > > > + filp_close(file, owner); > > > cond_resched(); > > > spin_lock(&files->file_lock); > > > } > > > @@ -1080,6 +1084,7 @@ static int do_dup2(struct files_struct *files, > > > struct file *file, unsigned fd, unsigned flags) > > > __releases(&files->file_lock) > > > { > > > + fl_owner_t owner = file_lock_make_thread_owner(files); > > > struct file *tofree; > > > struct fdtable *fdt; > > > > > > @@ -1111,7 +1116,7 @@ __releases(&files->file_lock) > > > spin_unlock(&files->file_lock); > > > > > > if (tofree) > > > - filp_close(tofree, files); > > > + filp_close(tofree, owner); > > > > > > return fd; > > > > > > diff --git a/fs/locks.c b/fs/locks.c > > > index 607f94a0e789..e8b67f87e0ee 100644 > > > --- a/fs/locks.c > > > +++ b/fs/locks.c > > > @@ -331,6 +331,8 @@ EXPORT_SYMBOL_GPL(locks_owner_has_blockers); > > > /* Free a lock which is not in use. */ > > > void locks_free_lock(struct file_lock *fl) > > > { > > > + if (fl->fl_file && file_lock_is_thread_owner(fl->fl_owner)) > > > + fput(fl->fl_file); > > > locks_release_private(fl); > > > kmem_cache_free(filelock_cache, fl); > > > } > > > @@ -384,7 +386,10 @@ void locks_copy_lock(struct file_lock *new, struct file_lock *fl) > > > > > > locks_copy_conflock(new, fl); > > > > > > - new->fl_file = fl->fl_file; > > > + if (file_lock_is_thread_owner(new->fl_owner)) > > > + new->fl_file = get_file(fl->fl_file); > > > + else > > > + new->fl_file = fl->fl_file; > > > new->fl_ops = fl->fl_ops; > > > > > > if (fl->fl_ops) { > > > @@ -488,13 +493,14 @@ static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl, > > > } else > > > fl->fl_end = OFFSET_MAX; > > > > > > - fl->fl_owner = current->files; > > > + fl->fl_owner = file_lock_make_thread_owner(current->files); > > > fl->fl_pid = current->tgid; > > > - fl->fl_file = filp; > > > + fl->fl_file = get_file(filp); > > > fl->fl_flags = FL_POSIX; > > > fl->fl_ops = NULL; > > > fl->fl_lmops = NULL; > > > > > > + > > > return assign_type(fl, l->l_type); > > > } > > > > > > @@ -2243,6 +2249,7 @@ int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock *flock) > > > > > > fl->fl_flags |= FL_OFDLCK; > > > fl->fl_owner = filp; > > > + fput(filp); > > > } > > > > > > error = vfs_test_lock(filp, fl); > > > @@ -2376,6 +2383,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd, > > > cmd = F_SETLK; > > > file_lock->fl_flags |= FL_OFDLCK; > > > file_lock->fl_owner = filp; > > > + fput(filp); > > > break; > > > case F_OFD_SETLKW: > > > error = -EINVAL; > > > @@ -2385,6 +2393,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd, > > > cmd = F_SETLKW; > > > file_lock->fl_flags |= FL_OFDLCK; > > > file_lock->fl_owner = filp; > > > + fput(filp); > > > fallthrough; > > > case F_SETLKW: > > > file_lock->fl_flags |= FL_SLEEP; > > > @@ -2450,6 +2459,7 @@ int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 *flock) > > > cmd = F_GETLK64; > > > fl->fl_flags |= FL_OFDLCK; > > > fl->fl_owner = filp; > > > + fput(filp); > > > } > > > > > > error = vfs_test_lock(filp, fl); > > > @@ -2499,6 +2509,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd, > > > cmd = F_SETLK64; > > > file_lock->fl_flags |= FL_OFDLCK; > > > file_lock->fl_owner = filp; > > > + fput(filp); > > > break; > > > case F_OFD_SETLKW: > > > error = -EINVAL; > > > @@ -2508,6 +2519,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd, > > > cmd = F_SETLKW64; > > > file_lock->fl_flags |= FL_OFDLCK; > > > file_lock->fl_owner = filp; > > > + fput(filp); > > > fallthrough; > > > case F_SETLKW64: > > > file_lock->fl_flags |= FL_SLEEP; > > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > > index e654435f1651..d7d81962a863 100644 > > > --- a/include/linux/fs.h > > > +++ b/include/linux/fs.h > > > @@ -1028,6 +1028,20 @@ static inline struct file *get_file(struct file *f) > > > /* legacy typedef, should eventually be removed */ > > > typedef void *fl_owner_t; > > > > > > +/* > > > + * Set the last significant bit to 1 to mark that > > > + * we have get a reference of the fl->fl_file. > > > + */ > > > +static inline fl_owner_t file_lock_make_thread_owner(fl_owner_t owner) > > > +{ > > > + return (fl_owner_t)((unsigned long)owner | 1UL); > > > +} > > > + > > > +static inline bool file_lock_is_thread_owner(fl_owner_t owner) > > > +{ > > > + return ((unsigned long)owner & 1UL); > > > +} > > > + > > > struct file_lock; > > > > > > struct file_lock_operations { > > > diff --git a/io_uring/openclose.c b/io_uring/openclose.c > > > index 67178e4bb282..5a12cdf7f8d0 100644 > > > --- a/io_uring/openclose.c > > > +++ b/io_uring/openclose.c > > > @@ -212,6 +212,7 @@ int io_close_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) > > > int io_close(struct io_kiocb *req, unsigned int issue_flags) > > > { > > > struct files_struct *files = current->files; > > > + fl_owner_t owner = file_lock_make_thread_owner(files); > > > struct io_close *close = io_kiocb_to_cmd(req, struct io_close); > > > struct fdtable *fdt; > > > struct file *file; > > > @@ -247,7 +248,7 @@ int io_close(struct io_kiocb *req, unsigned int issue_flags) > > > goto err; > > > > > > /* No ->flush() or already async, safely close from here */ > > > - ret = filp_close(file, current->files); > > > + ret = filp_close(file, owner); > > > err: > > > if (ret < 0) > > > req_set_fail(req); > > I think this is the wrong approach to fixing this. It also looks like > > you could hit a similar problem with OFD locks and this patch wouldn't > > address that issue. > > For the OFD locks they will set the 'file' struct as the owner just as > the flock does, it should be okay and I don't think it has this issue if > my understanding is correct here. > They set the the owner to "file", but they don't hold a reference to it. With OFD locks, the file is what holds references to the lock, not the reverse. > > The real bug seems to be that ceph_fl_release_lock dereferences fl_file, > > at a point when it shouldn't rely on that being valid. Most filesystems > > stash some info in fl->fl_u if they need to do bookkeeping after > > releasing a lock. Perhaps ceph should be doing something similar? > > This is the 'filp' memory in filp_close(filp, ...): > > crash> file.f_path.dentry,f_inode 0xffff952d7ab46200 > f_path.dentry = 0xffff9521b121cb40 > f_inode = 0xffff951f3ea33550, > > We can see the 'f_inode' is pointing to the correct inode memory. > > > > While later in 'ceph_fl_release_lock()': > > 41 static void ceph_fl_release_lock(struct file_lock *fl) > 42 { > 43 struct ceph_file_info *fi = fl->fl_file->private_data; > 44 struct inode *inode = file_inode(fl->fl_file); > 45 struct ceph_inode_info *ci = ceph_inode(inode); > 46 atomic_dec(&fi->num_locks); > 47 if (atomic_dec_and_test(&ci->i_filelock_ref)) { > 48 /* clear error when all locks are released */ > 49 spin_lock(&ci->i_ceph_lock); > 50 ci->i_ceph_flags &= ~CEPH_I_ERROR_FILELOCK; > 51 spin_unlock(&ci->i_ceph_lock); > 52 } > 53 } > You only need the inode for most of this. The exception is fi->num_locks, so you may need to test for that in a different way. > It crashed in Line#47 and the 'fl->fl_file' memory is: > > crash> file.f_path.dentry,f_inode 0xffff952d4ebd8a00 > f_path.dentry = 0x0 > f_inode = 0x0, > > Please NOTE: the 'filp' and 'fl->fl_file' are two different 'file struct'. > Yep, I understand the bug. I just don't like the proposed fix. :) > Can we fix this by using 'fl->fl_u' here ? > Probably. You could take and hold an inode reference in there, and maybe add a function that looks at whether there are any locks held against a particular file, rather than trying to count locks in ceph_file_info. > I was also thinking I could just call the 'get_file(file)' in > ceph_lock() and then in ceph_fl_release_lock() release the reference > counter. How about this ? > That may work too, though again, I'd be worried about cyclical dependencies, particularly with OFD locks. If the lock holds a reference to the file, then can the file's refcount ever go to zero if the lock is never explicitly released? I think not. You may also need to consider flock locks too, since they have similar ownership semantics to OFD locks. -- Jeff Layton <jlayton@xxxxxxxxxx>
