CVE-2023-54295

In the Linux kernel, the following vulnerability has been resolved:

mtd: spi-nor: Fix shift-out-of-bounds in spi_nor_set_erase_type

spi_nor_set_erase_type() was used either to set or to mask out an erase type. When we used it to mask out an erase type a shift-out-of-bounds was hit: UBSAN: shift-out-of-bounds in drivers/mtd/spi-nor/core.c:2237:24 shift exponent 4294967295 is too large for 32-bit type 'int'

The setting of the size_{shift, mask} and of the opcode are unnecessary when the erase size is zero, as throughout the code just the erase size is considered to determine whether an erase type is supported or not. Setting the opcode to 0xFF was wrong too as nobody guarantees that 0xFF is an unused opcode. Thus when masking out an erase type, just set the erase size to zero. This will fix the shift-out-of-bounds.

[ta: refine changes, new commit message, fix compilation error]

An undefined behavior bug was fixed in spi_nor_set_erase_type() where masking out an erase type could trigger a shift-out-of-bounds (UBSAN) due to an invalid shift exponent. Triggering the issue typically depends on SPI NOR/SFDP-derived parameters during device initialization (or privileged driver/module handling), making exploitation by an unprivileged local user unlikely on default systems. The most realistic impact is kernel warning/crash (DoS) in sanitized/debug configurations rather than a reliable escalation primitive.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.