Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:io_uring/rw: fix missing NOWAIT check for O_DIRECT start writeWhen io_uring starts a write, it'll call kiocb_start_write() to bump thesuper block rwsem, preventing any freezes from happening while thatwrite is in-flight. The freeze side will grab that rwsem for writing,excluding any new writers from happening and waiting for existing writesto finish. But io_uring unconditionally uses kiocb_start_write(), whichwill block if someone is currently attempting to freeze the mount point.This causes a deadlock where freeze is waiting for previous writes tocomplete, but the previous writes cannot complete, as the task that issupposed to complete them is blocked waiting on starting a new write.This results in the following stuck trace showing that dependency withthe write blocked starting a new write:task:fio             state:D stack:0     pid:886   tgid:886   ppid:876Call 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+0x168/0x170INFO: task fsfreeze:7364 blocked for more than 15 seconds.      Not tainted 6.12.0-rc5-00063-g76aaf945701c #7963with the attempting freezer stuck trying to grab the rwsem:task:fsfreeze        state:D stack:0     pid:7364  tgid:7364  ppid:995Call 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+0x168/0x170Fix this by having the io_uring side honor IOCB_NOWAIT, and only attempt ablocking grab of the super block rwsem if it isn't set. For normal issuewhere IOCB_NOWAIT would always be set, this returns -EAGAIN which willhave io_uring core issue a blocking attempt of the write. That will inturn also get completions run, ensuring forward progress.Since freezing requires CAP_SYS_ADMIN in the first place, this isn'tsomething that can be triggered by a regular user.

CREATE(Triage):(User=admin) CVE-2024-53052 (https://nvd.nist.gov/vuln/detail/CVE-2024-53052)

CVEs

• CVE-2024-53052