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Fix alignment of bootconfig

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GRUB may align the init ramdisk size to 4 bytes, the magic number at the
 end of the init ramdisk that denotes bootconfig is attached may not be at
 the exact end of the ramdisk. The kernel needs to check back at least 4
 bytes.
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Merge tag 'trace-v5.10-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull bootconfig fix from Steven Rostedt:
 "Fix alignment of bootconfig

  GRUB may align the init ramdisk size to 4 bytes, the magic number at
  the end of the init ramdisk that denotes bootconfig is attached may
  not be at the exact end of the ramdisk. The kernel needs to check back
  at least 4 bytes"

* tag 'trace-v5.10-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  bootconfig: Extend the magic check range to the preceding 3 bytes
This commit is contained in:
Linus Torvalds 2020-11-13 09:36:10 -08:00
commit 6186313d06
1 changed files with 12 additions and 2 deletions
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14
init/main.c
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@ -269,14 +269,24 @@ static void * __init get_boot_config_from_initrd(u32 *_size, u32 *_csum)
u32 size, csum;
char *data;
u32 *hdr;
int i;
if (!initrd_end)
return NULL;
data = (char *)initrd_end - BOOTCONFIG_MAGIC_LEN;
if (memcmp(data, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN))
return NULL;
/*
* Since Grub may align the size of initrd to 4, we must
* check the preceding 3 bytes as well.
*/
for (i = 0; i < 4; i++) {
if (!memcmp(data, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN))
goto found;
data--;
}
return NULL;
found:
hdr = (u32 *)(data - 8);
size = hdr[0];
csum = hdr[1];