On Wed, Nov 23, 2022 at 03:44:54PM +0100, Daniel Kiper wrote:
> On Wed, Nov 23, 2022 at 02:40:21PM +0800, Gary Lin via Grub-devel wrote:
> > Per "man 5 cpio", the namesize in the cpio header includes the trailing
> > NULL byte of the pathname and the pathname is followed by NULL bytes, but
>
> s/NULL/NUL/ and below please...
>
Will fix in v2.
> > the current implementation excludes the trailing NULL byte when making
> > the newc header plus the pathname. Although make_header() would pad the
> > pathname string, the padding won't happen when strlen(name) +
> > sizeof(struct newc_head) is a multiple of 4, and the non-NULL-terminated
> > pathname may lead to unexpected results.
> >
> > For example, when loading linux with the following command:
> >
> > linux /boot/vmlinuz
> > initrd newc:test12:/boot/test12 /boot/initrd
> >
> > Since strlen("test12") + sizeof(struct newc_head) is 116 = 29 * 4, there
> > is no padding for the pathname, and the following error may show during
> > linux boot:
> >
> > Initramfs unpacking failed: ZSTD-compressed data is trunc
> >
> > To avoid the potential problems, this commit includes the NULL byte when
> > calling make_header() and adjusts the initrd size accordingly.
> >
> > Signed-off-by: Gary Lin <g...@suse.com>
> > ---
> > grub-core/loader/linux.c | 16 +++++++++-------
> > 1 file changed, 9 insertions(+), 7 deletions(-)
> >
> > diff --git a/grub-core/loader/linux.c b/grub-core/loader/linux.c
> > index 830360172..2b26d293f 100644
> > --- a/grub-core/loader/linux.c
> > +++ b/grub-core/loader/linux.c
> > @@ -127,12 +127,14 @@ insert_dir (const char *name, struct dir **root,
> > n->name = grub_strndup (cb, ce - cb);
> > if (ptr)
> > {
> > + char *tmp_name = grub_strndup (name, ce - name);
>
> Why is this needed?
Because I need the extra '\0' for make_header(). For example, if "name"
is "dir123/file", insert_dir() only sends 'd''i''r''1''2''3' to
make_header() to create the header like this:
00000070 30 37 30 37 30 31 32 31 38 33 32 41 37 43 30 30 |07070121832A7C00|
00000080 30 30 34 31 45 44 30 30 30 30 30 33 45 38 30 30 |0041ED000003E800|
00000090 30 30 30 30 36 34 30 30 30 30 30 30 30 33 36 33 |0000640000000363|
000000a0 37 37 32 44 43 38 30 30 30 30 30 30 30 30 30 30 |772DC80000000000|
000000b0 30 30 30 30 30 38 30 30 30 30 30 30 31 33 30 30 |0000080000001300|
000000c0 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 |0000000000000000|
000000d0 30 30 30 30 30 36 30 30 30 30 30 30 30 30 64 69 |00000600000000di|
000000e0 72 31 32 33 30 37 30 37 30 31 31 31 34 44 37 46 |r123070701114D7F|
^
end of "dir123"
As you can see, the pathname is ended without '\0', and it violates the
cpio format. If we give make_header() the extra '\0':
00000070 30 37 30 37 30 31 32 31 38 33 32 41 37 43 30 30 |07070121832A7C00|
00000080 30 30 34 31 45 44 30 30 30 30 30 33 45 38 30 30 |0041ED000003E800|
00000090 30 30 30 30 36 34 30 30 30 30 30 30 30 33 36 33 |0000640000000363|
000000a0 37 37 32 44 43 38 30 30 30 30 30 30 30 30 30 30 |772DC80000000000|
000000b0 30 30 30 30 30 38 30 30 30 30 30 30 31 33 30 30 |0000080000001300|
000000c0 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 |0000000000000000|
000000d0 30 30 30 30 30 37 30 30 30 30 30 30 30 30 64 69 |00000700000000di|
000000e0 72 31 32 33 00 00 00 00 30 37 30 37 30 31 31 31 |r123....07070111|
There are 3 more NUL bytes appended, and the user can safely read the
pathname without a further check.
> And if it is needed you have to check for NULL here.
Okay. Will add the check in v2.
> I do not mention that formatting is broken too. You use spaces instead
> of tabs here and below.
>
I thought the indentation is 2-space without tab. Will convert 8 spaces
into one tab.
> > grub_dprintf ("linux", "Creating directory %s, %s\n", name, ce);
> > - ptr = make_header (ptr, name, ce - name,
> > + ptr = make_header (ptr, tmp_name, ce - name + 1,
> > 040777, 0);
> > + grub_free (tmp_name);
> > }
> > if (grub_add (*size,
> > - ALIGN_UP ((ce - (char *) name)
> > + ALIGN_UP ((ce - (char *) name + 1)
> > + sizeof (struct newc_head), 4),
> > size))
> > {
> > @@ -191,7 +193,7 @@ grub_initrd_init (int argc, char *argv[],
> > grub_initrd_close (initrd_ctx);
> > return grub_errno;
> > }
> > - name_len = grub_strlen (initrd_ctx->components[i].newc_name);
> > + name_len = grub_strlen (initrd_ctx->components[i].newc_name) + 1;
> > if (grub_add (initrd_ctx->size,
> > ALIGN_UP (sizeof (struct newc_head) + name_len, 4),
> > &initrd_ctx->size) ||
> > @@ -205,7 +207,7 @@ grub_initrd_init (int argc, char *argv[],
> > {
> > if (grub_add (initrd_ctx->size,
> > ALIGN_UP (sizeof (struct newc_head)
> > - + sizeof ("TRAILER!!!") - 1, 4),
> > + + sizeof ("TRAILER!!!"), 4),
>
> This change looks strange and begs for explanation in the patch.
>
The adjustment is to match the change of "TRAILER!!!" below.
> > &initrd_ctx->size))
> > goto overflow;
> > free_dir (root);
> > @@ -233,7 +235,7 @@ grub_initrd_init (int argc, char *argv[],
> > initrd_ctx->size = ALIGN_UP (initrd_ctx->size, 4);
> > if (grub_add (initrd_ctx->size,
> > ALIGN_UP (sizeof (struct newc_head)
> > - + sizeof ("TRAILER!!!") - 1, 4),
> > + + sizeof ("TRAILER!!!"), 4),
>
> Ditto and bellow...
>
> > &initrd_ctx->size))
> > goto overflow;
> > free_dir (root);
> > @@ -304,7 +306,7 @@ grub_initrd_load (struct grub_linux_initrd_context
> > *initrd_ctx,
> > }
> > else if (newc)
> > {
> > - ptr = make_header (ptr, "TRAILER!!!", sizeof ("TRAILER!!!") - 1,
> > + ptr = make_header (ptr, "TRAILER!!!", sizeof ("TRAILER!!!"),
> > 0, 0);
The "TRAILER!!!" header should count the NUL byte, not ignore it.
Gary Lin
> > free_dir (root);
> > root = 0;
> > @@ -327,7 +329,7 @@ grub_initrd_load (struct grub_linux_initrd_context
> > *initrd_ctx,
> > {
> > grub_memset (ptr, 0, ALIGN_UP_OVERHEAD (cursize, 4));
> > ptr += ALIGN_UP_OVERHEAD (cursize, 4);
> > - ptr = make_header (ptr, "TRAILER!!!", sizeof ("TRAILER!!!") - 1, 0,
> > 0);
> > + ptr = make_header (ptr, "TRAILER!!!", sizeof ("TRAILER!!!"), 0, 0);
>
> Daniel
>
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> Grub-devel@gnu.org
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