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posixshm: fix setting of shm_flags

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Noted in D24652, we currently set shmfd->shm_flags on every
shm_open()/shm_open2(). This wasn't properly thought out; one shouldn't be
able to specify incompatible flags on subsequent opens of non-anon shm.

Move setting of shm_flags explicitly to the two places shmfd are created, as
we do with seals, and validate when we're opening a pre-existing mapping
that we've either passed no flags or we've passed the exact same flags as
the first time.

Reviewed by:	kib, markj
Differential Revision:	https://reviews.freebsd.org/D26242
This commit is contained in:
Kyle Evans 2020-08-31 15:07:15 +00:00
parent 641b7baa5b
commit 5dd47b52e5
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=364990
1 changed files with 4 additions and 1 deletions
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5
sys/kern/uipc_shm.c
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@ -833,6 +833,7 @@ kern_shm_open2(struct thread *td, const char *userpath, int flags, mode_t mode,
}
shmfd = shm_alloc(td->td_ucred, cmode);
shmfd->shm_seals = initial_seals;
shmfd->shm_flags = shmflags;
} else {
error = shm_copyin_path(td, userpath, &path);
if (error != 0) {
@ -855,6 +856,7 @@ kern_shm_open2(struct thread *td, const char *userpath, int flags, mode_t mode,
#endif
shmfd = shm_alloc(td->td_ucred, cmode);
shmfd->shm_seals = initial_seals;
shmfd->shm_flags = shmflags;
shm_insert(path, fnv, shmfd);
#ifdef MAC
}
@ -898,6 +900,8 @@ kern_shm_open2(struct thread *td, const char *userpath, int flags, mode_t mode,
else if ((flags & (O_CREAT | O_EXCL)) ==
(O_CREAT | O_EXCL))
error = EEXIST;
else if (shmflags != 0 && shmflags != shmfd->shm_flags)
error = EINVAL;
else {
#ifdef MAC
error = mac_posixshm_check_open(td->td_ucred,
@ -947,7 +951,6 @@ kern_shm_open2(struct thread *td, const char *userpath, int flags, mode_t mode,
}
}
shmfd->shm_flags = shmflags;
finit(fp, FFLAGS(flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
td->td_retval[0] = fd;