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FreeBSD: Fix RLIMIT_FSIZE handling for block cloning

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ZFS implements copy_file_range(2) using block cloning when possible.
This implementation must respect the RLIMIT_FSIZE limit.

zfs_clone_range() already checks the limit, so it is safe to remove this
check in zfs_freebsd_copy_file_range().  Moreover, the removed check
produces false positives: the length passed to copy_file_range(2) may be
larger than the input file size; as the man page notes, "for best
performance, call copy_file_range() with the largest len value
possible."  In particular, some existing code passes SSIZE_MAX there.

The check in zfs_clone_range() clamps the length to the input file's
size before checking, but the removed check uses the caller supplied
length, so something like

$ echo a > /tmp/foo
$ limits -f 1024 cat /tmp/foo > /tmp/bar

fails because FreeBSD's cat(1) uses copy_file_range(2) in the manner
described above.

Reported-by: Philip Paeps <philip@FreeBSD.org>
Signed-off-by: Mark Johnston <markj@FreeBSD.org>

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Allan Jude <allan@klarasystems.com>
Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
This commit is contained in:
Mark Johnston 2024-07-23 10:20:46 -04:00 committed by Tony Hutter
parent 1f5bf91a85
commit dea8fabf73
1 changed files with 0 additions and 7 deletions
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7
module/os/freebsd/zfs/zfs_vnops_os.c
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@ -6072,7 +6072,6 @@ zfs_freebsd_copy_file_range(struct vop_copy_file_range_args *ap)
struct vnode *invp = ap->a_invp;
struct vnode *outvp = ap->a_outvp;
struct mount *mp;
struct uio io;
int error;
uint64_t len = *ap->a_lenp;
@ -6120,12 +6119,6 @@ zfs_freebsd_copy_file_range(struct vop_copy_file_range_args *ap)
goto out_locked;
#endif
io.uio_offset = *ap->a_outoffp;
io.uio_resid = *ap->a_lenp;
error = vn_rlimit_fsize(outvp, &io, ap->a_fsizetd);
if (error != 0)
goto out_locked;
error = zfs_clone_range(VTOZ(invp), ap->a_inoffp, VTOZ(outvp),
ap->a_outoffp, &len, ap->a_outcred);
if (error == EXDEV || error == EAGAIN || error == EINVAL ||