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Detect too-small device: error rather than underflow/crash 

For 1.x metadata, when the user requested creation of an array on
component devices that were too small even to hold the superblock,
an undetected integer wraparound (underflow) resulted in an enormous
computed size which resulted in various follow-on errors such as
floating-point exception.

This patch detects this condition, prints a reasonable diagnostic
message, and refuses to continue.

Signed-off-by: David Favro <dfavro@meta-dynamic.com>
Signed-off-by: Jes Sorensen <jsorensen@fb.com>
This commit is contained in:
David Favro 2020-05-23 08:24:59 -04:00 committed by Jes Sorensen
parent 7758ada9f3
commit 2cf0433063
1 changed files with 14 additions and 5 deletions
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19
super1.c
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@ -2753,6 +2753,7 @@ static int validate_geometry1(struct supertype *st, int level,
unsigned long long ldsize, devsize;
int bmspace;
unsigned long long headroom;
unsigned long long overhead;
int fd;
if (level == LEVEL_CONTAINER) {
@ -2785,10 +2786,6 @@ static int validate_geometry1(struct supertype *st, int level,
close(fd);
devsize = ldsize >> 9;
if (devsize < 24) {
*freesize = 0;
return 0;
}
/* creating: allow suitable space for bitmap or PPL */
if (consistency_policy == CONSISTENCY_POLICY_PPL)
@ -2829,15 +2826,27 @@ static int validate_geometry1(struct supertype *st, int level,
case 0: /* metadata at end. Round down and subtract space to reserve */
devsize = (devsize & ~(4ULL*2-1));
/* space for metadata, bblog, bitmap/ppl */
devsize -= 8*2 + 8 + bmspace;
overhead = 8*2 + 8 + bmspace;
if (devsize < overhead) /* detect underflow */
goto dev_too_small_err;
devsize -= overhead;
break;
case 1:
case 2:
if (devsize < data_offset) /* detect underflow */
goto dev_too_small_err;
devsize -= data_offset;
break;
}
*freesize = devsize;
return 1;
/* Error condition, device cannot even hold the overhead. */
dev_too_small_err:
fprintf(stderr, "device %s is too small (%lluK) for "
"required metadata!\n", subdev, devsize>>1);
*freesize = 0;
return 0;
}
void *super1_make_v0(struct supertype *st, struct mdinfo *info, mdp_super_t *sb0)