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From 2cf0433063203fca10d26629c9e090b51fb1d806 Mon Sep 17 00:00:00 2001
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From: David Favro <dfavro@meta-dynamic.com>
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Date: Sat, 23 May 2020 08:24:59 -0400
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Subject: [PATCH 083/108] Detect too-small device: error rather than
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underflow/crash
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For 1.x metadata, when the user requested creation of an array on
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component devices that were too small even to hold the superblock,
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an undetected integer wraparound (underflow) resulted in an enormous
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computed size which resulted in various follow-on errors such as
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floating-point exception.
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This patch detects this condition, prints a reasonable diagnostic
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message, and refuses to continue.
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Signed-off-by: David Favro <dfavro@meta-dynamic.com>
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Signed-off-by: Jes Sorensen <jsorensen@fb.com>
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---
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super1.c | 19 ++++++++++++++-----
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1 file changed, 14 insertions(+), 5 deletions(-)
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diff --git a/super1.c b/super1.c
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index e0d80be..7664883 100644
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--- a/super1.c
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+++ b/super1.c
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@@ -2753,6 +2753,7 @@ static int validate_geometry1(struct supertype *st, int level,
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unsigned long long ldsize, devsize;
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int bmspace;
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unsigned long long headroom;
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+ unsigned long long overhead;
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int fd;
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if (level == LEVEL_CONTAINER) {
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@@ -2785,10 +2786,6 @@ static int validate_geometry1(struct supertype *st, int level,
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close(fd);
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devsize = ldsize >> 9;
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- if (devsize < 24) {
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- *freesize = 0;
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- return 0;
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- }
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/* creating: allow suitable space for bitmap or PPL */
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if (consistency_policy == CONSISTENCY_POLICY_PPL)
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@@ -2829,15 +2826,27 @@ static int validate_geometry1(struct supertype *st, int level,
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case 0: /* metadata at end. Round down and subtract space to reserve */
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devsize = (devsize & ~(4ULL*2-1));
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/* space for metadata, bblog, bitmap/ppl */
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- devsize -= 8*2 + 8 + bmspace;
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+ overhead = 8*2 + 8 + bmspace;
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+ if (devsize < overhead) /* detect underflow */
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+ goto dev_too_small_err;
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+ devsize -= overhead;
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break;
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case 1:
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case 2:
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+ if (devsize < data_offset) /* detect underflow */
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+ goto dev_too_small_err;
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devsize -= data_offset;
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break;
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}
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*freesize = devsize;
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return 1;
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+
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+/* Error condition, device cannot even hold the overhead. */
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+dev_too_small_err:
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+ fprintf(stderr, "device %s is too small (%lluK) for "
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+ "required metadata!\n", subdev, devsize>>1);
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+ *freesize = 0;
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+ return 0;
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}
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void *super1_make_v0(struct supertype *st, struct mdinfo *info, mdp_super_t *sb0)
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--
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2.7.5
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