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Message-ID: <2f1fe2fe57f39ab420c7855584ae7b6bb85a7692.camel@kernel.org>
Date: Mon, 07 Nov 2022 05:33:14 -0500
From: Jeff Layton <jlayton@...nel.org>
To: xiubli@...hat.com, viro@...iv.linux.org.uk, chuck.lever@...cle.com
Cc: axboe@...nel.dk, asml.silence@...il.com,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
io-uring@...r.kernel.org, ceph-devel@...r.kernel.org,
mchangir@...hat.com, idryomov@...il.com, lhenriques@...e.de,
gfarnum@...hat.com
Subject: Re: [RFC PATCH] fs/lock: increase the filp's reference for
Posix-style locks
On Mon, 2022-11-07 at 17:52 +0800, xiubli@...hat.com wrote:
> From: Xiubo Li <xiubli@...hat.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@...hat.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.
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@...nel.org>
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