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sysvshm: pass relevant uap members as arguments

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Alter shmget_allocate_segment and shmget_existing to take the values
they want from struct shmget_args rather than passing the struct
around.  In general, uap structures should only be the interface to
sys_<foo> functions.

This makes on small functional change and records the allocated space
rather than the requested space.  If this turns out to be a problem (e.g.
if software tries to find undersized segments by exact size rather than
using keys), we can correct that easily.

Reviewed by:	kib
Obtained from:	CheriBSD
MFC after:	1 week
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D27077
This commit is contained in:
Brooks Davis 2020-11-03 19:14:03 +00:00
parent 7abf30d339
commit 19647e76fc
1 changed files with 18 additions and 18 deletions
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36
sys/kern/sysv_shm.c
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@ -111,11 +111,6 @@ FEATURE(sysv_shm, "System V shared memory segments support");
static MALLOC_DEFINE(M_SHM, "shm", "SVID compatible shared memory segments");
static int shmget_allocate_segment(struct thread *td,
struct shmget_args *uap, int mode);
static int shmget_existing(struct thread *td, struct shmget_args *uap,
int mode, int segnum);
#define SHMSEG_FREE 0x0200
#define SHMSEG_REMOVED 0x0400
#define SHMSEG_ALLOCATED 0x0800
@ -134,6 +129,10 @@ static void shm_deallocate_segment(struct shmid_kernel *);
static int shm_find_segment_by_key(struct prison *, key_t);
static struct shmid_kernel *shm_find_segment(struct prison *, int, bool);
static int shm_delete_mapping(struct vmspace *vm, struct shmmap_state *);
static int shmget_allocate_segment(struct thread *td, key_t key, size_t size,
int mode);
static int shmget_existing(struct thread *td, size_t size, int shmflg,
int mode, int segnum);
static void shmrealloc(void);
static int shminit(void);
static int sysvshm_modload(struct module *, int, void *);
@ -659,7 +658,7 @@ sys_shmctl(struct thread *td, struct shmctl_args *uap)
}
static int
shmget_existing(struct thread *td, struct shmget_args *uap, int mode,
shmget_existing(struct thread *td, size_t size, int shmflg, int mode,
int segnum)
{
struct shmid_kernel *shmseg;
@ -671,35 +670,34 @@ shmget_existing(struct thread *td, struct shmget_args *uap, int mode,
KASSERT(segnum >= 0 && segnum < shmalloced,
("segnum %d shmalloced %d", segnum, shmalloced));
shmseg = &shmsegs[segnum];
if ((uap->shmflg & (IPC_CREAT | IPC_EXCL)) == (IPC_CREAT | IPC_EXCL))
if ((shmflg & (IPC_CREAT | IPC_EXCL)) == (IPC_CREAT | IPC_EXCL))
return (EEXIST);
#ifdef MAC
error = mac_sysvshm_check_shmget(td->td_ucred, shmseg, uap->shmflg);
error = mac_sysvshm_check_shmget(td->td_ucred, shmseg, shmflg);
if (error != 0)
return (error);
#endif
if (uap->size != 0 && uap->size > shmseg->u.shm_segsz)
if (size != 0 && size > shmseg->u.shm_segsz)
return (EINVAL);
td->td_retval[0] = IXSEQ_TO_IPCID(segnum, shmseg->u.shm_perm);
return (0);
}
static int
shmget_allocate_segment(struct thread *td, struct shmget_args *uap, int mode)
shmget_allocate_segment(struct thread *td, key_t key, size_t size, int mode)
{
struct ucred *cred = td->td_ucred;
struct shmid_kernel *shmseg;
vm_object_t shm_object;
int i, segnum;
size_t size;
SYSVSHM_ASSERT_LOCKED();
if (uap->size < shminfo.shmmin || uap->size > shminfo.shmmax)
if (size < shminfo.shmmin || size > shminfo.shmmax)
return (EINVAL);
if (shm_nused >= shminfo.shmmni) /* Any shmids left? */
return (ENOSPC);
size = round_page(uap->size);
size = round_page(size);
if (shm_committed + btoc(size) > shminfo.shmall)
return (ENOMEM);
if (shm_last_free < 0) {
@ -755,10 +753,10 @@ shmget_allocate_segment(struct thread *td, struct shmget_args *uap, int mode)
shmseg->u.shm_perm.cuid = shmseg->u.shm_perm.uid = cred->cr_uid;
shmseg->u.shm_perm.cgid = shmseg->u.shm_perm.gid = cred->cr_gid;
shmseg->u.shm_perm.mode = (mode & ACCESSPERMS) | SHMSEG_ALLOCATED;
shmseg->u.shm_perm.key = uap->key;
shmseg->u.shm_perm.key = key;
shmseg->u.shm_perm.seq = (shmseg->u.shm_perm.seq + 1) & 0x7fff;
shmseg->cred = crhold(cred);
shmseg->u.shm_segsz = uap->size;
shmseg->u.shm_segsz = size;
shmseg->u.shm_cpid = td->td_proc->p_pid;
shmseg->u.shm_lpid = shmseg->u.shm_nattch = 0;
shmseg->u.shm_atime = shmseg->u.shm_dtime = 0;
@ -791,16 +789,18 @@ sys_shmget(struct thread *td, struct shmget_args *uap)
mode = uap->shmflg & ACCESSPERMS;
SYSVSHM_LOCK();
if (uap->key == IPC_PRIVATE) {
error = shmget_allocate_segment(td, uap, mode);
error = shmget_allocate_segment(td, uap->key, uap->size, mode);
} else {
segnum = shm_find_segment_by_key(td->td_ucred->cr_prison,
uap->key);
if (segnum >= 0)
error = shmget_existing(td, uap, mode, segnum);
error = shmget_existing(td, uap->size, uap->shmflg,
mode, segnum);
else if ((uap->shmflg & IPC_CREAT) == 0)
error = ENOENT;
else
error = shmget_allocate_segment(td, uap, mode);
error = shmget_allocate_segment(td, uap->key,
uap->size, mode);
}
SYSVSHM_UNLOCK();
return (error);