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initramfs_test: add filename padding test case

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Confirm that cpio filenames with multiple trailing zeros (accounted for
in namesize) extract successfully.

Signed-off-by: David Disseldorp <ddiss@suse.de>
Acked-by: Nicolas Schier <nsc@kernel.org>
Link: https://lore.kernel.org/r/20250819032607.28727-9-ddiss@suse.de
[nathan: Fix duplicate filesize initialization, reported at
         https://lore.kernel.org/202508200304.wF1u78il-lkp@intel.com/]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
This commit is contained in:
David Disseldorp
2025-08-19 13:05:51 +10:00
committed by Nathan Chancellor
parent 5467e85508
commit 6da752f55b
1 changed files with 66 additions and 1 deletions
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67
init/initramfs_test.c
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@@ -45,8 +45,11 @@ static size_t fill_cpio(struct initramfs_test_cpio *cs, size_t csz, char *out)
c->mtime, c->filesize, c->devmajor, c->devminor,
c->rdevmajor, c->rdevminor, c->namesize, c->csum,
c->fname) + 1;
pr_debug("packing (%zu): %.*s\n", thislen, (int)thislen, pos);
off += thislen;
if (thislen != CPIO_HDRLEN + c->namesize)
pr_debug("padded to: %u\n", CPIO_HDRLEN + c->namesize);
off += CPIO_HDRLEN + c->namesize;
while (off & 3)
out[off++] = '\0';
@@ -383,6 +386,67 @@ static void __init initramfs_test_many(struct kunit *test)
kfree(cpio_srcbuf);
}
/*
* An initramfs filename is namesize in length, including the zero-terminator.
* A filename can be zero-terminated prior to namesize, with the remainder used
* as padding. This can be useful for e.g. alignment of file data segments with
* a 4KB filesystem block, allowing for extent sharing (reflinks) between cpio
* source and destination. This hack works with both GNU cpio and initramfs, as
* long as PATH_MAX isn't exceeded.
*/
static void __init initramfs_test_fname_pad(struct kunit *test)
{
char *err;
size_t len;
struct file *file;
char fdata[] = "this file data is aligned at 4K in the archive";
struct test_fname_pad {
char padded_fname[4096 - CPIO_HDRLEN];
char cpio_srcbuf[CPIO_HDRLEN + PATH_MAX + 3 + sizeof(fdata)];
} *tbufs = kzalloc(sizeof(struct test_fname_pad), GFP_KERNEL);
struct initramfs_test_cpio c[] = { {
.magic = "070701",
.ino = 1,
.mode = S_IFREG | 0777,
.uid = 0,
.gid = 0,
.nlink = 1,
.mtime = 1,
.filesize = sizeof(fdata),
.devmajor = 0,
.devminor = 1,
.rdevmajor = 0,
.rdevminor = 0,
/* align file data at 4K archive offset via padded fname */
.namesize = 4096 - CPIO_HDRLEN,
.csum = 0,
.fname = tbufs->padded_fname,
.data = fdata,
} };
memcpy(tbufs->padded_fname, "padded_fname", sizeof("padded_fname"));
len = fill_cpio(c, ARRAY_SIZE(c), tbufs->cpio_srcbuf);
err = unpack_to_rootfs(tbufs->cpio_srcbuf, len);
KUNIT_EXPECT_NULL(test, err);
file = filp_open(c[0].fname, O_RDONLY, 0);
if (IS_ERR(file)) {
KUNIT_FAIL(test, "open failed");
goto out;
}
/* read back file contents into @cpio_srcbuf and confirm match */
len = kernel_read(file, tbufs->cpio_srcbuf, c[0].filesize, NULL);
KUNIT_EXPECT_EQ(test, len, c[0].filesize);
KUNIT_EXPECT_MEMEQ(test, tbufs->cpio_srcbuf, c[0].data, len);
fput(file);
KUNIT_EXPECT_EQ(test, init_unlink(c[0].fname), 0);
out:
kfree(tbufs);
}
/*
* The kunit_case/_suite struct cannot be marked as __initdata as this will be
* used in debugfs to retrieve results after test has run.
@@ -394,6 +458,7 @@ static struct kunit_case __refdata initramfs_test_cases[] = {
KUNIT_CASE(initramfs_test_csum),
KUNIT_CASE(initramfs_test_hardlink),
KUNIT_CASE(initramfs_test_many),
KUNIT_CASE(initramfs_test_fname_pad),
{},
};