diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c index 9e9010f0f62a..0c1c6b86a03f 100644 --- a/sys/kern/kern_descrip.c +++ b/sys/kern/kern_descrip.c @@ -1512,11 +1512,19 @@ fdgrowtable(struct filedesc *fdp, int nfd) memcpy(nmap, omap, NDSLOTS(onfiles) * sizeof(*omap)); /* update the pointers and counters */ - fdp->fd_nfiles = nnfiles; memcpy(ntable, otable, onfiles * sizeof(ntable[0])); fdp->fd_ofiles = ntable; fdp->fd_map = nmap; + /* + * In order to have a valid pattern for fget_unlocked() + * fdp->fd_nfiles might be the last member to be updated, otherwise + * fget_unlocked() consumers may reference a new, higher value for + * fdp->fd_nfiles before to access the fdp->fd_ofiles array, + * resulting in OOB accesses. + */ + atomic_store_rel_int(&fdp->fd_nfiles, nnfiles); + /* * Do not free the old file table, as some threads may still * reference entries within it. Instead, place it on a freelist @@ -2308,7 +2316,11 @@ fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp, int error; #endif - if (fd < 0 || fd >= fdp->fd_nfiles) + /* + * Avoid reads reordering and then a first access to the + * fdp->fd_ofiles table which could result in OOB operation. + */ + if (fd < 0 || fd >= atomic_load_acq_int(&fdp->fd_nfiles)) return (EBADF); /* * Fetch the descriptor locklessly. We avoid fdrop() races by