Messages in this thread | | | Subject | Re: [RFC PATCH] fs/lock: increase the filp's reference for Posix-style locks | From | Xiubo Li <> | Date | Mon, 7 Nov 2022 20:03:10 +0800 |
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On 07/11/2022 18:33, Jeff Layton wrote: > On Mon, 2022-11-07 at 17:52 +0800, xiubli@redhat.com wrote: >> From: Xiubo Li <xiubli@redhat.com> >> >> 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@redhat.com> >> --- >> 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.
> 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 }
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'.
Can we fix this by using 'fl->fl_u' here ?
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 ?
Thanks!
- Xiubo
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