RE: [PATCH v9 1/1] efi: a misc char interface for user to update efi firmware

["Kweh, Hock Leong" <hock.leong.kweh@intel.com>]

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> -----Original Message-----
> From: Borislav Petkov [mailto:bp@alien8.de]
> Sent: Sunday, November 01, 2015 6:30 PM
> >
> > Example method to load the capsule binary:
> > cat firmware.bin > /dev/efi_capsule_loader
> 
> $ cat "some_dumb_file" > /dev/efi_capsule_loader Killed
> 
> and in dmesg:
> 
> [   34.033982] efi_capsule_loader: efi_capsule_flush: capsule upload not
> complete
> [   58.765683] ------------[ cut here ]------------
> [   58.769349] WARNING: CPU: 5 PID: 3904 at
> drivers/firmware/efi/capsule.c:83 efi_capsule_supported+0x103/0x150()
> [   58.775063] Modules linked in:
> [   58.776474] CPU: 5 PID: 3904 Comm: cat Not tainted 4.3.0-rc7+ #3
> [   58.779044] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> 1.7.5-20140531_083030-gandalf 04/01/2014
> [   58.783387]  ffffffff81957aa0 ffff880079793d78 ffffffff812cb2ea
> 0000000000000000
> [   58.786749]  ffff880079793db0 ffffffff81055981 00010102464c457f
> 0000000000000000
> [   58.790140]  0000000000401e3b 0000000000000001 ffff880078660704
> ffff880079793dc0
> [   58.793353] Call Trace:
> [   58.794343]  [<ffffffff812cb2ea>] dump_stack+0x4e/0x84
> [   58.796416]  [<ffffffff81055981>] warn_slowpath_common+0x91/0xd0
> [   58.798773]  [<ffffffff81055a7a>] warn_slowpath_null+0x1a/0x20
> [   58.800962]  [<ffffffff8157ae93>] efi_capsule_supported+0x103/0x150
> [   58.803292]  [<ffffffff8157d559>] efi_capsule_write+0x269/0x390
> [   58.805563]  [<ffffffff81183ef8>] __vfs_write+0x28/0xe0
> [   58.807591]  [<ffffffff81183e9a>] ? __vfs_read+0xaa/0xe0
> [   58.809612]  [<ffffffff811847d5>] vfs_write+0xb5/0x1a0
> [   58.811272]  [<ffffffff811a33be>] ? __fget_light+0x6e/0x90
> [   58.813073]  [<ffffffff81185412>] SyS_write+0x52/0xc0
> [   58.814720]  [<ffffffff816cff5b>] entry_SYSCALL_64_fastpath+0x16/0x73
> [   58.816665] ---[ end trace 94c0c141f9b0ec01 ]---
> [   58.818179] BUG: unable to handle kernel NULL pointer dereference at
> (null)
> [   58.820427] IP: [<          (null)>]           (null)
> [   58.820630] PGD 79af8067 PUD 79781067 PMD 0
> [   58.820630] Oops: 0010 [#1] PREEMPT SMP
> [   58.820630] Modules linked in:
> [   58.820630] CPU: 5 PID: 3904 Comm: cat Tainted: G        W       4.3.0-rc7+ #3
> [   58.820630] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> 1.7.5-20140531_083030-gandalf 04/01/2014
> [   58.820630] task: ffff8800771417c0 ti: ffff880079790000 task.ti:
> ffff880079790000
> [   58.820630] RIP: 0010:[<0000000000000000>]  [<          (null)>]           (null)
> [   58.820630] RSP: 0018:ffff880079793dc8  EFLAGS: 00010282
> [   58.820630] RAX: ffff88007a01b4e0 RBX: 00010102464c457f RCX:
> ffff880078660704
> [   58.820630] RDX: ffff880079793dd8 RSI: 0000000000000001 RDI:
> ffff880079793dd0
> [   58.820630] RBP: ffff880079793e08 R08: 0000000000000000 R09:
> 0000000000000000
> [   58.820630] R10: 0000000000000000 R11: 0000000000000001 R12:
> 0000000000000000
> [   58.820630] R13: 0000000000401e3b R14: 0000000000000001 R15:
> ffff880078660704
> [   58.820630] FS:  00007ffff7fe1700(0000) GS:ffff88007c000000(0000)
> knlGS:0000000000000000
> [   58.820630] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [   58.820630] CR2: 0000000000000000 CR3: 000000007ab90000 CR4:
> 00000000000406e0
> [   58.820630] Stack:
> [   58.820630]  ffffffff8157ae24 ffff88007a01b4e0 0000000000000002
> ffff880078660700
> [   58.820630]  ffff880077060000 0000000000001000 ffffea0001dc1800
> ffff880077060000
> [   58.820630]  ffff880079793e48 ffffffff8157d559 0000000000000402
> ffff8800799cbc00
> [   58.820630] Call Trace:
> [   58.820630]  [<ffffffff8157ae24>] ? efi_capsule_supported+0x94/0x150
> [   58.820630]  [<ffffffff8157d559>] efi_capsule_write+0x269/0x390
> [   58.820630]  [<ffffffff81183ef8>] __vfs_write+0x28/0xe0
> [   58.820630]  [<ffffffff81183e9a>] ? __vfs_read+0xaa/0xe0
> [   58.820630]  [<ffffffff811847d5>] vfs_write+0xb5/0x1a0
> [   58.820630]  [<ffffffff811a33be>] ? __fget_light+0x6e/0x90
> [   58.820630]  [<ffffffff81185412>] SyS_write+0x52/0xc0
> [   58.820630]  [<ffffffff816cff5b>] entry_SYSCALL_64_fastpath+0x16/0x73
> [   58.820630] Code:  Bad RIP value.
> [   58.820630] RIP  [<          (null)>]           (null)
> [   58.820630]  RSP <ffff880079793dc8>
> [   58.820630] CR2: 0000000000000000
> [   58.876221] ---[ end trace 94c0c141f9b0ec02 ]---
> 

Could you share me your dumb file? I did perform negative test, but I did
not get these dump stack in dmesg. Thanks.

> 
> Please integrate checkpatch into your workflow - it can be helpful
> sometimes:
> 
> WARNING: 'OCCURED' may be misspelled - perhaps 'OCCURRED'?
> #114: FILE: drivers/firmware/efi/efi-capsule-loader.c:22:
> +#define ERR_OCCURED -2
> 
> WARNING: 'OCCURED' may be misspelled - perhaps 'OCCURRED'?
> #132: FILE: drivers/firmware/efi/efi-capsule-loader.c:40:
> + *     Besides freeing the buffer pages, it also flagged an ERR_OCCURED
> 
> WARNING: 'OCCURED' may be misspelled - perhaps 'OCCURRED'?
> #144: FILE: drivers/firmware/efi/efi-capsule-loader.c:52:
> +       cap_info->index = ERR_OCCURED;
> 
> WARNING: Possible unnecessary 'out of memory' message
> #399: FILE: drivers/firmware/efi/efi-capsule-loader.c:307:
> +       if (!cap_info) {
> +               pr_debug("%s: kzalloc() failed\n", __func__);
> 

I did use checkpatch. May be my version is different. Will get the
latest version and run it again. Thanks.

> > +config EFI_CAPSULE_LOADER
> > +	tristate "EFI capsule loader"
> > +	depends on EFI
> > +	help
> > +	  This option exposes a loader interface "/dev/efi_capsule_loader"
> for
> > +	  user to load EFI capsule binary and update the EFI firmware through
> > +	  system reboot.
> 
> Make this:
> 
> 	... and update the EFI firmware. After a successful loading, a system
> 	reboot is required."
> 

Ok. Noted.

> >
> >  /**
> >   * efi_capsule_update - send a capsule to the firmware diff --git
> > a/drivers/firmware/efi/efi-capsule-loader.c
> > b/drivers/firmware/efi/efi-capsule-loader.c
> 
> All those files under drivers/firmware/efi/ are EFI stuff so this one doesn't
> need the "efi-" name prefix either. efi-pstore.c I'm looking at you too.
> 

Ok. Noted.

> > +
> > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> 
> I think this should be
> 
> #define pr_fmt(fmt) "EFI: " fmt
> 
> or something that all EFI code uses.
> 

Ok. Noted.

> > +
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/miscdevice.h>
> > +#include <linux/highmem.h>
> > +#include <linux/slab.h>
> > +#include <linux/mutex.h>
> > +#include <linux/efi.h>
> > +
> > +#define DEV_NAME "efi_capsule_loader"
> 
> Why a define if it is used only in one place? Just put the string there instead.

Ok. Noted.

> 
> > +#define UPLOAD_DONE -1
> 
> Isn't the fact that upload was finished a success message? If so, why is it a
> negative value?

This is to indicate an upload is done and pending for close(2). If a subsequence
write(2) perform, return error. Comments inputted by Matt and Andy.

> 
> > +#define ERR_OCCURED -2
> 
> WARNING: 'OCCURED' may be misspelled - perhaps 'OCCURRED'?
> #114: FILE: drivers/firmware/efi/efi-capsule-loader.c:22:
> +#define ERR_OCCURED -2
> 
> Ok, that should be enough review for now - I'll take a look at the rest once
> you've taken care of the splat above and those minor issues I pointed out.
> 
> Thanks.
> 

Thanks for the review.

Regards,
Wilson

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