initramfs: cleanup incomplete rootfs

Unpacking an external initrd may fail e.g. not enough memory. This leads to an incomplete rootfs because some files might be extracted already. Fixed by cleaning the rootfs so the kernel is not using an incomplete rootfs.

Signed-off-by David Engraf <[email protected]>

---
 init/initramfs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

init/initramfs.c +3 -4

index 640557788026..aa3a46cfcb4e 100644
@@ -548,7 +548,6 @@ static void __init free_initrd(void)
        initrd_end = 0;
 }
 
-#ifdef CONFIG_BLK_DEV_RAM
 #define BUF_SIZE 1024
 static void __init clean_rootfs(void)
 {

@@ -595,7 +594,6 @@ static void __init clean_rootfs(void)
        ksys_close(fd);
        kfree(buf);
 }
-#endif
 
 static int __init populate_rootfs(void)
 {

@@ -638,8 +636,10 @@ static int __init populate_rootfs(void)
                printk(KERN_INFO "Unpacking initramfs...\n");
                err = unpack_to_rootfs((char *)initrd_start,
                        initrd_end - initrd_start);
-               if (err)
+               if (err) {
                        printk(KERN_EMERG "Initramfs unpacking failed: %s\n", err);
+                       clean_rootfs();
+               }
                free_initrd();
 #endif
        }
--

2.17.1

Quoted 5 lines · David Engraf

Unpacking an external initrd may fail e.g. not enough memory. This leads to an incomplete rootfs because some files might be extracted already. Fixed by cleaning the rootfs so the kernel is not using an incomplete rootfs.

This breaks my setup where I have U-boot provided more size of initramfs than needed. This allows a bit of flexibility to increase or decrease initramfs compressed image without taking care of bootloader. The proper solution is to do this if we sure that we didn't get enough memory, otherwise I can't consider the error fatal to clean up rootfs.

Quoted 7 lines · On Fri, 8 Feb 2019 21:45:21 +0200 Andy Shevchenko <[email protected]>…

Quoted 5 lines · David Engraf

Unpacking an external initrd may fail e.g. not enough memory. This leads to an incomplete rootfs because some files might be extracted already. Fixed by cleaning the rootfs so the kernel is not using an incomplete rootfs.

Quoted 5 lines

This breaks my setup where I have U-boot provided more size of initramfs than needed. This allows a bit of flexibility to increase or decrease initramfs compressed image without taking care of bootloader. The proper solution is to do this if we sure that we didn't get enough memory, otherwise I can't consider the error fatal to clean up rootfs.

OK, thanks. Maybe David can suggest a fix - I'll queue up a revert meanwhile.

I don't really understand the failure. Why does an oversized initramfs cause unpack_to_rootfs() to fail?

Quoted 14 lines · Andrew Morton

Quoted 7 lines · On Fri, 8 Feb 2019 21:45:21 +0200 Andy Shevchenko <[email protected]>…

Quoted 5 lines · David Engraf

Unpacking an external initrd may fail e.g. not enough memory. This leads to an incomplete rootfs because some files might be extracted already. Fixed by cleaning the rootfs so the kernel is not using an incomplete rootfs.

Quoted 5 lines

This breaks my setup where I have U-boot provided more size of initramfs than needed. This allows a bit of flexibility to increase or decrease initramfs compressed image without taking care of bootloader. The proper solution is to do this if we sure that we didn't get enough memory, otherwise I can't consider the error fatal to clean up rootfs.

Quoted 5 lines

OK, thanks. Maybe David can suggest a fix - I'll queue up a revert meanwhile.

I don't really understand the failure. Why does an oversized initramfs cause unpack_to_rootfs() to fail?

In my case I have got "Junk in compressed archive". I don't know (I would check if needed) which exact condition I got since there are three places with this message. The file itself smaller than the size passed through bootparam. So, when decomression is finished (successfully!) we still have a garbarge in the memory which is not related to archive. Message per se is okay to have, though I consider this non-fatal.

Quoted 21 lines · Andy Shevchenko

Quoted 14 lines · Andrew Morton

Quoted 7 lines · On Fri, 8 Feb 2019 21:45:21 +0200 Andy Shevchenko <[email protected]>…

Quoted 5 lines · David Engraf

Unpacking an external initrd may fail e.g. not enough memory. This leads to an incomplete rootfs because some files might be extracted already. Fixed by cleaning the rootfs so the kernel is not using an incomplete rootfs.

Quoted 5 lines

This breaks my setup where I have U-boot provided more size of initramfs than needed. This allows a bit of flexibility to increase or decrease initramfs compressed image without taking care of bootloader. The proper solution is to do this if we sure that we didn't get enough memory, otherwise I can't consider the error fatal to clean up rootfs.

Quoted 5 lines

OK, thanks.  Maybe David can suggest a fix - I'll queue up a revert meanwhile.

I don't really understand the failure.  Why does an oversized initramfs cause unpack_to_rootfs() to fail?

Quoted 7 lines

In my case I have got "Junk in compressed archive". I don't know (I would check if needed) which exact condition I got  since there are three places with this message. The file itself smaller than the size passed through bootparam. So, when decomression is finished (successfully!) we still have a garbarge in the memory which is not related to archive. Message per se is okay to have, though I consider this non-fatal.

I can reproduce this special case. The unpacking decompresses the whole size instead of checking the archive size. I will have a look how to get the real archive size.

Quoted 34 lines · David Engraf

Quoted 32 lines · Andy Shevchenko

Quoted 17 lines · Andrew Morton

Quoted 9 lines · On Fri, 8 Feb 2019 21:45:21 +0200 Andy Shevchenko <[email protected]>…

Quoted 6 lines · David Engraf

Unpacking an external initrd may fail e.g. not enough memory. This leads
to an incomplete rootfs because some files might be extracted already. Fixed by cleaning the rootfs so the kernel is not using an incomplete rootfs.

Quoted 5 lines

This breaks my setup where I have U-boot provided more size of initramfs than needed. This allows a bit of flexibility to increase or decrease initramfs compressed image without taking care of bootloader. The proper solution is to do this if we sure that we didn't get enough memory, otherwise I can't consider the error fatal to clean up rootfs.

Quoted 5 lines

OK, thanks. Maybe David can suggest a fix - I'll queue up a revert meanwhile.

I don't really understand the failure. Why does an oversized initramfs cause unpack_to_rootfs() to fail?

In my case I have got "Junk in compressed archive". I don't know (I would check if needed) which exact condition I got since there are three places with this message. The file itself smaller than the size passed through bootparam. So, when decomression is finished (successfully!) we still have a garbarge in the memory which is not related to archive. Message per se is okay to have, though I consider this non-fatal.

Quoted 3 lines

I can reproduce this special case. The unpacking decompresses the whole size instead of checking the archive size. I will have a look how to get the real archive size.

I did some checks and manually increased the initramfs size but I always get the following kernel panic:

Kernel panic - not syncing: junk in compressed archive
---[ end Kernel panic - not syncing: junk in compressed archive

The panic was not introduced by my patch. Could you please check if you get a panic as well or is your rootfs just empty?

I also had a look at the decompression in unpack_to_rootfs(). This function already ensures unpacking only the real size of the archive. But it is called in a loop, thus it unpacks the first archive and then tries to unpack the reset of the data which are garbage in my case.

Is it intended to allow extracting multiple archives as rootfs?

If not
we could remove the loop and unpack only the first archive. Otherwise we could ignore errors when the first archive was extracted without errors.

Quoted 35 lines · David Engraf

Quoted 34 lines · David Engraf

Quoted 32 lines · Andy Shevchenko

Quoted 17 lines · Andrew Morton

Quoted 9 lines · On Fri, 8 Feb 2019 21:45:21 +0200 Andy Shevchenko <[email protected]>…

Quoted 6 lines · David Engraf

Unpacking an external initrd may fail e.g. not enough memory. This leads
to an incomplete rootfs because some files might be extracted already. Fixed by cleaning the rootfs so the kernel is not using an incomplete rootfs.

Quoted 5 lines

This breaks my setup where I have U-boot provided more size of initramfs than needed. This allows a bit of flexibility to increase or decrease initramfs compressed image without taking care of bootloader. The proper solution is to do this if we sure that we didn't get enough memory, otherwise I can't consider the error fatal to clean up rootfs.

Quoted 5 lines

OK, thanks. Maybe David can suggest a fix - I'll queue up a revert meanwhile.

I don't really understand the failure. Why does an oversized initramfs cause unpack_to_rootfs() to fail?

In my case I have got "Junk in compressed archive". I don't know (I would check if needed) which exact condition I got since there are three places with this message. The file itself smaller than the size passed through bootparam. So, when decomression is finished (successfully!) we still have a garbarge in the memory which is not related to archive. Message per se is okay to have, though I consider this non-fatal.

Quoted 6 lines

Quoted 3 lines

I can reproduce this special case. The unpacking decompresses the whole size instead of checking the archive size. I will have a look how to get the real archive size.

I did some checks and manually increased the initramfs size but I always get the following kernel panic:

We need to be on the same page here.
There are two sizes of initramfs compressed archive:
1) actual file size;
2) what is declared by boot loader and provided via boot parameters.

In my case I have the 2) bigger than the actual file size. Kernel decompresses the initramfs, prints an error that there is junk, which is understandable and continues to run init, etc.

Quoted 5 lines

Kernel panic - not syncing: junk in compressed archive
---[ end Kernel panic - not syncing: junk in compressed archive

The panic was not introduced by my patch. Could you please check if you get a panic as well or is your rootfs just empty?

Since your patch applied I get rootfs clean followed by inability to find working init. So, I have a panic with different reason.

Quoted 6 lines

I also had a look at the decompression in unpack_to_rootfs(). This function already ensures unpacking only the real size of the archive. But it is called in a loop, thus it unpacks the first archive and then tries to unpack the reset of the data which are garbage in my case.

Is it intended to allow extracting multiple archives as rootfs?

Yes. You can chain up to 64 archives IIRC.

Quoted 3 lines

If not
we could remove the loop and unpack only the first archive. Otherwise we could ignore errors when the first archive was extracted without errors.

Not the first one, but all the first one_s_. Means, that at least one, when it's first(!), is decompressed successfully.

Quoted 30 lines · Andy Shevchenko

Quoted 17 lines · David Engraf

Quoted 16 lines · David Engraf

Quoted 14 lines · Andy Shevchenko

Quoted 4 lines · Andrew Morton

Quoted 2 lines · On Fri, 8 Feb 2019 21:45:21 +0200 Andy Shevchenko <[email protected]>…

On Tue, Oct 30, 2018 at 5:22 PM David Engraf
<[email protected]> wrote:

In my case I have got "Junk in compressed archive". I don't know (I would check if needed) which exact condition I got since there are three places with this message. The file itself smaller than the size passed through bootparam. So, when decomression is finished (successfully!) we still have a garbarge in the memory which is not related to archive. Message per se is okay to have, though I consider this non-fatal.

Quoted 6 lines

Quoted 3 lines

I can reproduce this special case. The unpacking decompresses the whole size instead of checking the archive size. I will have a look how to get the real archive size.

I did some checks and manually increased the initramfs size but I always get the following kernel panic:

We need to be on the same page here.
There are two sizes of initramfs compressed archive:
1) actual file size;
2) what is declared by boot loader and provided via boot parameters.

Quoted 3 lines

In my case I have the 2) bigger than the actual file size. Kernel decompresses the initramfs, prints an error that there is junk, which is understandable and continues to run init, etc.

Ok got it. When the memory behind the actual file size is clear (0x0) the decompression doesn't complain and just ignores the padding. Any other data will be interpreted as a new archive and thus you'll see the error message.

Is it possible for you to fill the padding after the actual file size with 0x00 ?

Quoted 31 lines · David Engraf

Quoted 30 lines · Andy Shevchenko

Quoted 17 lines · David Engraf

Quoted 16 lines · David Engraf

Quoted 14 lines · Andy Shevchenko

Quoted 4 lines · Andrew Morton

Quoted 2 lines · On Fri, 8 Feb 2019 21:45:21 +0200 Andy Shevchenko <[email protected]>…

On Tue, Oct 30, 2018 at 5:22 PM David Engraf
<[email protected]> wrote:

In my case I have got "Junk in compressed archive". I don't know (I would check if needed) which exact condition I got since there are three places with this message. The file itself smaller than the size passed through bootparam. So, when decomression is finished (successfully!) we still have a garbarge in the memory which is not related to archive. Message per se is okay to have, though I consider this non-fatal.

Quoted 6 lines

Quoted 3 lines

I can reproduce this special case. The unpacking decompresses the whole size instead of checking the archive size. I will have a look how to get the real archive size.

I did some checks and manually increased the initramfs size but I always get the following kernel panic:

We need to be on the same page here.
There are two sizes of initramfs compressed archive:
1) actual file size;
2) what is declared by boot loader and provided via boot parameters.

Quoted 8 lines

Quoted 3 lines

In my case I have the 2) bigger than the actual file size. Kernel decompresses the initramfs, prints an error that there is junk, which is understandable and continues to run init, etc.

Ok got it. When the memory behind the actual file size is clear (0x0) the decompression doesn't complain and just ignores the padding. Any other data will be interpreted as a new archive and thus you'll see the error message.

Correct.

Quoted 2 lines

Is it possible for you to fill the padding after the actual file size with 0x00 ?

Not sure. This is boot loader realm. Even if I patch U-Boot, not every boot loader will guarantee this.
So, it's fragile to rely on data being 0x00 after actual archive.

Quoted 13 lines · Andy Shevchenko

Quoted 6 lines · David Engraf

On 11.02.19 at 12:40, Andy Shevchenko wrote:

Ok got it. When the memory behind the actual file size is clear (0x0) the decompression doesn't complain and just ignores the padding. Any other data will be interpreted as a new archive and thus you'll see the error message.

Correct.

Quoted 2 lines

Is it possible for you to fill the padding after the actual file size with 0x00 ?

Quoted 3 lines

Not sure. This is boot loader realm. Even if I patch U-Boot, not every boot loader will guarantee this.
So, it's fragile to rely on data being 0x00 after actual archive.

The problem is that the kernel expects another archive if there are data left. If these data do not contain a valid magic the kernel prints an error message which is correct.

I could make this error not critical and keep the rootfs, but it's still an error and unexpected.

You're using a modified bootloader which
reports a size larger than the file itself.

Other bootloader will use
the file size and report the correct size to the kernel.

So this
workaround is required by your setup only.

@Andrew: What do you think about that? Shall I create a workaround for the special case?

Quoted 18 lines · David Engraf

Quoted 16 lines · Andy Shevchenko

Quoted 6 lines · David Engraf

On 11.02.19 at 12:40, Andy Shevchenko wrote:

Ok got it. When the memory behind the actual file size is clear (0x0) the decompression doesn't complain and just ignores the padding. Any other data will be interpreted as a new archive and thus you'll see the error message.

Correct.

Quoted 2 lines

Is it possible for you to fill the padding after the actual file size with 0x00 ?

Not sure. This is boot loader realm. Even if I patch U-Boot, not every boot loader will guarantee this.
So, it's fragile to rely on data being 0x00 after actual archive.

Quoted 3 lines

The problem is that the kernel expects another archive if there are data left. If these data do not contain a valid magic the kernel prints an error message which is correct.

Agree.

Quoted 2 lines

I could make this error not critical and keep the rootfs, but it's still an error and unexpected.

I would rather call it a warning and continue.

Perhaps something like

static void warning(const char *msg)
{
...print warning...
return without assigning return value.
}

Quoted 17 lines · Andrew Morton

Quoted 7 lines · On Fri, 8 Feb 2019 21:45:21 +0200 Andy Shevchenko <[email protected]>…

Quoted 5 lines · David Engraf

Unpacking an external initrd may fail e.g. not enough memory. This leads to an incomplete rootfs because some files might be extracted already. Fixed by cleaning the rootfs so the kernel is not using an incomplete rootfs.

Quoted 5 lines

This breaks my setup where I have U-boot provided more size of initramfs than needed. This allows a bit of flexibility to increase or decrease initramfs compressed image without taking care of bootloader. The proper solution is to do this if we sure that we didn't get enough memory, otherwise I can't consider the error fatal to clean up rootfs.

OK, thanks. Maybe David can suggest a fix - I'll queue up a revert meanwhile.

Quoted 2 lines

I don't really understand the failure. Why does an oversized initramfs cause unpack_to_rootfs() to fail?

In my case I have got "Junk in compressed archive". I don't know (I would check if needed) which exact condition I got since there are three places with this message.

Quoted 21 lines · On Sat, 9 Feb 2019 12:35:03 +0200 Andy Shevchenko <[email protected]>…

Quoted 19 lines · Andrew Morton

Quoted 7 lines · On Fri, 8 Feb 2019 21:45:21 +0200 Andy Shevchenko <[email protected]>…

Quoted 5 lines · David Engraf

Unpacking an external initrd may fail e.g. not enough memory. This leads to an incomplete rootfs because some files might be extracted already. Fixed by cleaning the rootfs so the kernel is not using an incomplete rootfs.

Quoted 5 lines

This breaks my setup where I have U-boot provided more size of initramfs than needed. This allows a bit of flexibility to increase or decrease initramfs compressed image without taking care of bootloader. The proper solution is to do this if we sure that we didn't get enough memory, otherwise I can't consider the error fatal to clean up rootfs.

OK, thanks. Maybe David can suggest a fix - I'll queue up a revert meanwhile.

I don't really understand the failure. Why does an oversized initramfs cause unpack_to_rootfs() to fail?

Quoted 3 lines

In my case I have got "Junk in compressed archive". I don't know (I would check if needed) which exact condition I got since there are three places with this message.

Well that's a plain irritating screwup right there. Could someone please cook up a patch to give us three distinct (and hopefully more informative) error messages?