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zfs_cmd: reorganise zfs_cmd_t to match original size

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2aa3fbe761 extended zinject_record_t, and in doing so inadvertently
extended zfs_cmd_t, which broke compatibility with userspace tools
without the change.

This fixes that by using some of the unused space in zfs_cmd_t for the
extra fields. We also add an assert to trigger a compile error if the
size ever changes.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17367
This commit is contained in:
Rob Norris
2025-05-28 10:01:06 +10:00
committed by GitHub
parent 087d7d80c7
commit 06fa8f3f69
3 changed files with 164 additions and 87 deletions
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include/sys/zfs_ioctl.h
+30 -4
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@@ -534,10 +534,22 @@ typedef struct zfs_cmd {
zfs_share_t zc_share;
dmu_objset_stats_t zc_objset_stats;
struct drr_begin zc_begin_record;
zinject_record_t zc_inject_record;
uint32_t zc_defer_destroy;
uint32_t zc_flags;
uint64_t zc_action_handle;
/*
* zinject_record_t grew past its original size, which would push out
* the size of zfs_cmd_t. To adjust for this, we allow it to use the
* space after it, since those fields aren't used with ZFS_IOC_INJECT.
*/
union {
zinject_record_t zc_inject_record;
struct {
char zc_pad1[sizeof (zinject_record_t) - 16];
uint32_t zc_defer_destroy;
uint32_t zc_flags;
uint64_t zc_action_handle;
};
};
int zc_cleanup_fd;
uint8_t zc_simple;
uint8_t zc_pad[3]; /* alignment */
@@ -548,6 +560,20 @@ typedef struct zfs_cmd {
uint64_t zc_zoneid;
} zfs_cmd_t;
/*
* zfs_cmd_t (and by extension, it's member structs) must always be the same
* size. Changing it will break compatibility between the kernel module and the
* userspace tools.
*
* This test is convoluted because MAXPATHLEN and MAXNAMELEN can vary across
* platforms. We include them directly here, which means it won't trip if those
* ever change, but if that happens we likely have other things to worry about.
*/
#define _expected_zfs_cmd_size ((MAXPATHLEN*3)+MAXNAMELEN+1200)
_Static_assert(sizeof (zfs_cmd_t) == _expected_zfs_cmd_size,
"zfs_cmd_t has wrong size");
#undef _expected_zfs_cmd_size
typedef struct zfs_useracct {
char zu_domain[256];
uid_t zu_rid;