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. 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? -- Jeff Layton <jlayton@xxxxxxxxxx>
