From: Jens Axboe <axboe@kernel.dk> stable inclusion from stable-v5.10.230 commit 485d9232112b17f389b29497ff41b97b3189546b category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IB5KQC CVE: CVE-2024-53052 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- Commit 1d60d74e852647255bd8e76f5a22dc42531e4389 upstream. When io_uring starts a write, it'll call kiocb_start_write() to bump the super block rwsem, preventing any freezes from happening while that write is in-flight. The freeze side will grab that rwsem for writing, excluding any new writers from happening and waiting for existing writes to finish. But io_uring unconditionally uses kiocb_start_write(), which will block if someone is currently attempting to freeze the mount point. This causes a deadlock where freeze is waiting for previous writes to complete, but the previous writes cannot complete, as the task that is supposed to complete them is blocked waiting on starting a new write. This results in the following stuck trace showing that dependency with the write blocked starting a new write: task:fio state:D stack:0 pid:886 tgid:886 ppid:876 Call trace: __switch_to+0x1d8/0x348 __schedule+0x8e8/0x2248 schedule+0x110/0x3f0 percpu_rwsem_wait+0x1e8/0x3f8 __percpu_down_read+0xe8/0x500 io_write+0xbb8/0xff8 io_issue_sqe+0x10c/0x1020 io_submit_sqes+0x614/0x2110 __arm64_sys_io_uring_enter+0x524/0x1038 invoke_syscall+0x74/0x268 el0_svc_common.constprop.0+0x160/0x238 do_el0_svc+0x44/0x60 el0_svc+0x44/0xb0 el0t_64_sync_handler+0x118/0x128 el0t_64_sync+0x168/0x170 INFO: task fsfreeze:7364 blocked for more than 15 seconds. Not tainted 6.12.0-rc5-00063-g76aaf945701c #7963 with the attempting freezer stuck trying to grab the rwsem: task:fsfreeze state:D stack:0 pid:7364 tgid:7364 ppid:995 Call trace: __switch_to+0x1d8/0x348 __schedule+0x8e8/0x2248 schedule+0x110/0x3f0 percpu_down_write+0x2b0/0x680 freeze_super+0x248/0x8a8 do_vfs_ioctl+0x149c/0x1b18 __arm64_sys_ioctl+0xd0/0x1a0 invoke_syscall+0x74/0x268 el0_svc_common.constprop.0+0x160/0x238 do_el0_svc+0x44/0x60 el0_svc+0x44/0xb0 el0t_64_sync_handler+0x118/0x128 el0t_64_sync+0x168/0x170 Fix this by having the io_uring side honor IOCB_NOWAIT, and only attempt a blocking grab of the super block rwsem if it isn't set. For normal issue where IOCB_NOWAIT would always be set, this returns -EAGAIN which will have io_uring core issue a blocking attempt of the write. That will in turn also get completions run, ensuring forward progress. Since freezing requires CAP_SYS_ADMIN in the first place, this isn't something that can be triggered by a regular user. Cc: stable@vger.kernel.org # 5.10+ Reported-by: Peter Mann <peter.mann@sh.cz> Link: https://lore.kernel.org/io-uring/38c94aec-81c9-4f62-b44e-1d87f5597644@sh.cz Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org> Conflicts: fs/io_uring.c [Context differences.] Signed-off-by: Baokun Li <libaokun1@huawei.com> --- fs/io_uring.c | 36 +++++++++++++++++++++++------------- 1 file changed, 23 insertions(+), 13 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 411b7491f3f5..96255b816d71 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -3174,6 +3174,27 @@ static int io_write_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe, return io_rw_prep_async(req, WRITE, force_nonblock); } +static bool io_kiocb_start_write(struct io_kiocb *req, struct kiocb *kiocb) +{ + struct inode *inode; + bool ret; + + if (!(req->flags & REQ_F_ISREG)) + return true; + + inode = file_inode(kiocb->ki_filp); + if (!(kiocb->ki_flags & IOCB_NOWAIT)) { + __sb_start_write(inode->i_sb, SB_FREEZE_WRITE, true); + __sb_writers_release(inode->i_sb, SB_FREEZE_WRITE); + return true; + } + + ret = sb_start_write_trylock(inode->i_sb); + if (ret) + __sb_writers_release(inode->i_sb, SB_FREEZE_WRITE); + return ret; +} + static int io_write(struct io_kiocb *req, bool force_nonblock, struct io_comp_state *cs) { @@ -3209,19 +3230,8 @@ static int io_write(struct io_kiocb *req, bool force_nonblock, unsigned long nr_segs = iter.nr_segs; ssize_t ret2; - /* - * Open-code file_start_write here to grab freeze protection, - * which will be released by another thread in - * io_complete_rw(). Fool lockdep by telling it the lock got - * released so that it doesn't complain about the held lock when - * we return to userspace. - */ - if (req->flags & REQ_F_ISREG) { - __sb_start_write(file_inode(req->file)->i_sb, - SB_FREEZE_WRITE, true); - __sb_writers_release(file_inode(req->file)->i_sb, - SB_FREEZE_WRITE); - } + if (unlikely(!io_kiocb_start_write(req, kiocb))) + goto copy_iov; kiocb->ki_flags |= IOCB_WRITE; if (req->file->f_op->write_iter) -- 2.46.1