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Intentionally allow ZFS_READONLY in zfs_write

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ZFS_READONLY represents the "DOS R/O" attribute.
When that flag is set, we should behave as if write access
were not granted by anything in the ACL.  In particular:
We _must_ allow writes after opening the file r/w, then
setting the DOS R/O attribute, and writing some more.
(Similar to how you can write after fchmod(fd, 0444).)

Restore these semantics which were lost on FreeBSD when refactoring
zfs_write.  To my knowledge Linux does not actually expose this flag,
but we'll need it to eventually so I've added the supporting checks.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #11693
This commit is contained in:
Ryan Moeller 2021-03-07 12:31:52 -05:00 committed by GitHub
parent e7a06356c1
commit 4b2e20824b
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2 changed files with 25 additions and 7 deletions
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26
module/os/linux/zfs/zfs_acl.c
View File

@ -2214,13 +2214,11 @@ zfs_zaccess_dataset_check(znode_t *zp, uint32_t v4_mode)
} }
/* /*
* Only check for READONLY on non-directories. * Intentionally allow ZFS_READONLY through here.
* See zfs_zaccess_common().
*/ */
if ((v4_mode & WRITE_MASK_DATA) && if ((v4_mode & WRITE_MASK_DATA) &&
((!S_ISDIR(ZTOI(zp)->i_mode) && (zp->z_pflags & ZFS_IMMUTABLE)) {
(zp->z_pflags & (ZFS_READONLY | ZFS_IMMUTABLE))) ||
(S_ISDIR(ZTOI(zp)->i_mode) &&
(zp->z_pflags & ZFS_IMMUTABLE)))) {
return (SET_ERROR(EPERM)); return (SET_ERROR(EPERM));
} }
@ -2434,6 +2432,24 @@ zfs_zaccess_common(znode_t *zp, uint32_t v4_mode, uint32_t *working_mode,
return (0); return (0);
} }
/*
* Note: ZFS_READONLY represents the "DOS R/O" attribute.
* When that flag is set, we should behave as if write access
* were not granted by anything in the ACL. In particular:
* We _must_ allow writes after opening the file r/w, then
* setting the DOS R/O attribute, and writing some more.
* (Similar to how you can write after fchmod(fd, 0444).)
*
* Therefore ZFS_READONLY is ignored in the dataset check
* above, and checked here as if part of the ACL check.
* Also note: DOS R/O is ignored for directories.
*/
if ((v4_mode & WRITE_MASK_DATA) &&
S_ISDIR(ZTOI(zp)->i_mode) &&
(zp->z_pflags & ZFS_READONLY)) {
return (SET_ERROR(EPERM));
}
return (zfs_zaccess_aces_check(zp, working_mode, B_FALSE, cr)); return (zfs_zaccess_aces_check(zp, working_mode, B_FALSE, cr));
} }

6
module/zfs/zfs_vnops.c
View File

@ -350,9 +350,11 @@ zfs_write(znode_t *zp, zfs_uio_t *uio, int ioflag, cred_t *cr)
} }
/* /*
* If immutable or not appending then return EPERM * If immutable or not appending then return EPERM.
* Intentionally allow ZFS_READONLY through here.
* See zfs_zaccess_common()
*/ */
if ((zp->z_pflags & (ZFS_IMMUTABLE | ZFS_READONLY)) || if ((zp->z_pflags & ZFS_IMMUTABLE) ||
((zp->z_pflags & ZFS_APPENDONLY) && !(ioflag & O_APPEND) && ((zp->z_pflags & ZFS_APPENDONLY) && !(ioflag & O_APPEND) &&
(zfs_uio_offset(uio) < zp->z_size))) { (zfs_uio_offset(uio) < zp->z_size))) {
ZFS_EXIT(zfsvfs); ZFS_EXIT(zfsvfs);