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The expression (ctx.bounds.height - combining_glyphs[i]->height) / 2 may evaluate to a very big invalid value even if both ctx.bounds.height and combining_glyphs[i]->height are small integers. For example, if ctx.bounds.height is 10 and combining_glyphs[i]->height is 12, this expression evaluates to 2147483647 (expected -1). This is because coordinates are allowed to be negative but ctx.bounds.height is an unsigned int. So, the subtraction operates on unsigned ints and underflows to a very big value. The division makes things even worse. The quotient is still an invalid value even if converted back to int. This patch fixes the problem by casting ctx.bounds.height to int. As a result the subtraction will operate on int and grub_uint16_t which will be promoted to an int. So, the underflow will no longer happen. Other uses of ctx.bounds.height (and ctx.bounds.width) are also casted to int, to ensure coordinates are always calculated on signed integers. Fixes: CVE-2022-3775 Reported-by: Daniel Axtens <dja@axtens.net> Signed-off-by: Zhang Boyang <zhangboyang.id@gmail.com> 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. See the file MAINTAINERS for information about the GRUB maintainers, etc. If you found a security vulnerability in the GRUB please check the SECURITY file to get more information how to properly report this kind of bugs to the maintainers. 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'