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Commit 9acdcbf32542 (use single quotes in menuentry setparams command) says that expressing a quoted single quote will require 3 characters. It actually requires (and always did require!) 4 characters: str: a'b => a'\''b len: 3 => 6 (2 for the letters + 4 for the quote) This leads to not allocating enough memory and thus out of bounds writes that have been observed to cause heap corruption. Allocate 4 bytes for each single quote. Commit 22e7dbb2bb81 (Fix quoting in legacy parser.) does the same quoting, but it adds 3 as extra overhead on top of the single byte that the quote already needs. So it's correct. Fixes: 9acdcbf32542 (use single quotes in menuentry setparams command) Fixes: CVE-2021-20233 Reported-by: Daniel Axtens <dja@axtens.net> Signed-off-by: Daniel Axtens <dja@axtens.net> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This is GRUB 2, the second version of the GRand Unified Bootloader. GRUB 2 is rewritten from scratch to make GNU GRUB cleaner, safer, more robust, more powerful, and more portable. See the file NEWS for a description of recent changes to GRUB 2. See the file INSTALL for instructions on how to build and install the GRUB 2 data and program files. Please visit the official web page of GRUB 2, for more information. The URL is <http://www.gnu.org/software/grub/grub.html>. More extensive documentation is available in the Info manual, accessible using 'info grub' after building and installing GRUB 2. There are a number of important user-visible differences from the first version of GRUB, now known as GRUB Legacy. For a summary, please see: info grub Introduction 'Changes from GRUB Legacy'