md: do overflow check for sb->bblog_shift in super_1_load()

Overview

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

md: do overflow check for sb->bblog_shift in super_1_load()

In super_1_load(), sb->bblog_shift is an __u8 type value loaded from on- disk superblock. It is used for badblocks API badblocks_set() by the following sequence,

1930 rdev->badblocks.shift = sb->bblog_shift; 1931 for (i = 0 ; i < (sectors << (9-3)) ; i++, bbp++) { 1932 u64 bb = le64_to_cpu(*bbp); 1933 int count = bb & (0x3ff); 1934 u64 sector = bb >> 10; 1935 sector <<= sb->bblog_shift; 1936 count <<= sb->bblog_shift; 1937 if (bb + 1 == 0) 1938 break; 1939 if (!badblocks_set(&rdev->badblocks, sector, count, 1)) 1940 return -EINVAL; 1941 }

bb->bblog_shit is in range of 0-255, variable sector is 64bit width, for an invalid bb->bblog_shit, it is possible to make sector be overflowed by the following calculation, 1935 sector <<= sb->bblog_shift; Then in turn when call badblocks_set() at line 1939 with the invalid rdev->badblocks.shift set at line 1930, may result an overflow inside _badblocks_clear() in block/badblocks.c.

Although there are many places to call badblocks APIs, the non-zero shift value is only used in super_1_load(), other places always use 0 as the shift value. Therefore it is unnecessary to do a general shift value overflow check inside badblock API, and just check here as the caller.

This may avoid unnecessary check, make the badblocks API code more simple and elegant.

Affected

• Linux >= 2699b67223aca6b1450fc2f72e40fada952afc85 < 94c820d99a4305d4ded41a97ed37ec7d26c56e7f
• Linux >= 2699b67223aca6b1450fc2f72e40fada952afc85 < 573fb68105fdc6a127ba6069e58a0d2aff3c9f93
• Linux >= 2699b67223aca6b1450fc2f72e40fada952afc85 < 323f3a056dbccb39a642ebde642044a680f3a6d6
• Linux >= 2699b67223aca6b1450fc2f72e40fada952afc85 < 0a03f9541c06fda64301dcf94f376f07ce2cc396
• Linux >= 2699b67223aca6b1450fc2f72e40fada952afc85 < 75d15738fd33a782606d0dc80cfeff47edf2ddd8
• Linux >= 2699b67223aca6b1450fc2f72e40fada952afc85 < 3b097416b4cff77285c1f472fc2c4058d8a7554f
• Linux >= 2699b67223aca6b1450fc2f72e40fada952afc85 < df7d4d011d5ace20699ea948712f09f9ac08924f
• Linux >= 2699b67223aca6b1450fc2f72e40fada952afc85 < 35d522bd32462afcf1981dab6da8a9256c26c1e0
• Linux 3.1

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.