From: Amir Goldstein amir73il@gmail.com

stable inclusion from stable-v5.10.230 commit f83a32351efd6c6676fdabd5ab0e680500bc48e0 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=...

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Commit ed0360bbab72b829437b67ebb2f9cfac19f59dfe upstream.

aio, io_uring, cachefiles and overlayfs, all open code an ugly variant of file_{start,end}_write() to silence lockdep warnings.

Create helpers for this lockdep dance so we can use the helpers in all the callers.

Suggested-by: Jan Kara jack@suse.cz Signed-off-by: Amir Goldstein amir73il@gmail.com Reviewed-by: Jan Kara jack@suse.cz Reviewed-by: Jens Axboe axboe@kernel.dk Message-Id: 20230817141337.1025891-4-amir73il@gmail.com Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Baokun Li libaokun1@huawei.com --- include/linux/fs.h | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h index afbd97e44f0b..4ce9c03d40cd 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1762,6 +1762,41 @@ static inline bool sb_start_intwrite_trylock(struct super_block *sb) return __sb_start_write_trylock(sb, SB_FREEZE_FS); }

+/** + * kiocb_start_write - get write access to a superblock for async file io + * @iocb: the io context we want to submit the write with + * + * This is a variant of sb_start_write() for async io submission. + * Should be matched with a call to kiocb_end_write(). + */ +static inline void kiocb_start_write(struct kiocb *iocb) +{ + struct inode *inode = file_inode(iocb->ki_filp); + + sb_start_write(inode->i_sb); + /* + * Fool lockdep by telling it the lock got released so that it + * doesn't complain about the held lock when we return to userspace. + */ + __sb_writers_release(inode->i_sb, SB_FREEZE_WRITE); +} + +/** + * kiocb_end_write - drop write access to a superblock after async file io + * @iocb: the io context we sumbitted the write with + * + * Should be matched with a call to kiocb_start_write(). + */ +static inline void kiocb_end_write(struct kiocb *iocb) +{ + struct inode *inode = file_inode(iocb->ki_filp); + + /* + * Tell lockdep we inherited freeze protection from submission thread. + */ + __sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE); + sb_end_write(inode->i_sb); +}

extern bool inode_owner_or_capable(const struct inode *inode);

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=...

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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 Signed-off-by: Baokun Li libaokun1@huawei.com --- io_uring/io_uring.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index e5ff11af63ea..4d69fb4cf803 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -3661,6 +3661,25 @@ static int io_write_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) return io_prep_rw(req, sqe, WRITE); }

+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; + if (!(kiocb->ki_flags & IOCB_NOWAIT)) { + kiocb_start_write(kiocb); + return true; + } + + inode = file_inode(kiocb->ki_filp); + 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, unsigned int issue_flags) { struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs; @@ -3704,8 +3723,8 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags) if (unlikely(ret)) goto out_free;

- if (req->flags & REQ_F_ISREG) - kiocb_start_write(kiocb); + if (unlikely(!io_kiocb_start_write(req, kiocb))) + goto copy_iov; kiocb->ki_flags |= IOCB_WRITE;

if (req->file->f_op->write_iter)