The branch releng/14.5 has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=9c7f4633c57a3c13b2c0b60090ffa9b14d1c1ce9
commit 9c7f4633c57a3c13b2c0b60090ffa9b14d1c1ce9 Author: Mark Johnston <[email protected]> AuthorDate: 2026-08-24 18:15:38 +0000 Commit: Mark Johnston <[email protected]> CommitDate: 2026-08-24 19:04:38 +0000 posixshm: Fix a TOCTOU race in the FIOSSHMLPGCNF handler The check for whether shm_lp_psind was assigned was unlocked. This race can be exploited to create an object with psind==2 but with only pagesizes[1] worth of pages populated. This in turn can be used to escalate privileges. Fix this by acquiring the rangelock earlier. In shm_mmap_large(), assert that we hold the rangelock. In shm_write(), annotate an unlocked load of shm_lp_psind. Approved by: re (cperciva) Approved by: so Security: FreeBSD-SA-26:63.posixshm Security: CVE-2026-58094 Reported by: tsune of GMO Cybersecurity by Ierae, Inc. working with TrendAI Zero Day Initiative Reviewed by: kib Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D59104 --- sys/kern/uipc_shm.c | 27 +++++++++++++++++---------- sys/sys/mman.h | 2 +- 2 files changed, 18 insertions(+), 11 deletions(-) diff --git a/sys/kern/uipc_shm.c b/sys/kern/uipc_shm.c index 9c2f91ffe347..3cb4b9734066 100644 --- a/sys/kern/uipc_shm.c +++ b/sys/kern/uipc_shm.c @@ -506,8 +506,6 @@ shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred, if (error) return (error); #endif - if (shm_largepage(shmfd) && shmfd->shm_lp_psind == 0) - return (EINVAL); foffset_lock_uio(fp, uio, flags); if (uio->uio_resid > OFF_MAX - uio->uio_offset) { /* @@ -529,7 +527,9 @@ shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred, else rl_cookie = shm_rangelock_wlock(shmfd, uio->uio_offset, MAX(newsize, uio->uio_offset)); - if ((shmfd->shm_seals & F_SEAL_WRITE) != 0) { + if (shm_largepage(shmfd) && shmfd->shm_lp_psind == 0) { + error = EINVAL; + } else if ((shmfd->shm_seals & F_SEAL_WRITE) != 0) { error = EPERM; } else { error = 0; @@ -586,18 +586,23 @@ shm_ioctl(struct file *fp, u_long com, void *data, struct ucred *active_cred, if (!shm_largepage(shmfd)) return (ENOTTY); conf = data; + rl_cookie = shm_rangelock_wlock(shmfd, 0, OFF_MAX); if (shmfd->shm_lp_psind != 0 && - conf->psind != shmfd->shm_lp_psind) + conf->psind != shmfd->shm_lp_psind) { + shm_rangelock_unlock(shmfd, rl_cookie); return (EINVAL); + } if (conf->psind <= 0 || conf->psind >= MAXPAGESIZES || - pagesizes[conf->psind] == 0) + pagesizes[conf->psind] == 0) { + shm_rangelock_unlock(shmfd, rl_cookie); return (EINVAL); + } if (conf->alloc_policy != SHM_LARGEPAGE_ALLOC_DEFAULT && conf->alloc_policy != SHM_LARGEPAGE_ALLOC_NOWAIT && - conf->alloc_policy != SHM_LARGEPAGE_ALLOC_HARD) + conf->alloc_policy != SHM_LARGEPAGE_ALLOC_HARD) { + shm_rangelock_unlock(shmfd, rl_cookie); return (EINVAL); - - rl_cookie = shm_rangelock_wlock(shmfd, 0, OFF_MAX); + } shmfd->shm_lp_psind = conf->psind; shmfd->shm_lp_alloc_policy = conf->alloc_policy; shmfd->shm_object->un_pager.phys.data_val = conf->psind; @@ -1591,7 +1596,7 @@ out: static int shm_mmap_large(struct shmfd *shmfd, vm_map_t map, vm_offset_t *addr, vm_size_t size, vm_prot_t prot, vm_prot_t max_prot, int flags, - vm_ooffset_t foff, struct thread *td) + vm_ooffset_t foff, struct thread *td, void *rl_cookie) { struct vmspace *vms; vm_map_entry_t next_entry, prev_entry; @@ -1599,6 +1604,8 @@ shm_mmap_large(struct shmfd *shmfd, vm_map_t map, vm_offset_t *addr, int docow, error, rv, try; bool curmap; + rangelock_cookie_assert(rl_cookie, RA_LOCKED); + if (shmfd->shm_lp_psind == 0) return (EINVAL); @@ -1763,7 +1770,7 @@ shm_mmap(struct file *fp, vm_map_t map, vm_offset_t *addr, vm_size_t objsize, if (shm_largepage(shmfd)) { writecnt = false; error = shm_mmap_large(shmfd, map, addr, objsize, prot, - maxprot, flags, foff, td); + maxprot, flags, foff, td, rl_cookie); } else { if (writecnt) { vm_pager_update_writecount(shmfd->shm_object, 0, diff --git a/sys/sys/mman.h b/sys/sys/mman.h index d444f02d3c89..0717edf6a926 100644 --- a/sys/sys/mman.h +++ b/sys/sys/mman.h @@ -291,7 +291,7 @@ struct shmfd { int shm_flags; int shm_seals; - /* largepage config */ + /* largepage config, synchronized by the rangelock */ int shm_lp_psind; int shm_lp_alloc_policy; };
