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Properly determine length for on-disk TOAST values

author Tomas Vondra <tomas.vondra@postgresql.org>

2019年11月16日 01:40:02 +0000 (02:40 +0100)

committer Tomas Vondra <tomas.vondra@postgresql.org>

2019年11月16日 02:07:11 +0000 (03:07 +0100)

In detoast_attr_slice, VARSIZE_ANY was used to compute compressed length
of on-disk TOAST values. That's incorrect, because the varlena value may
be just a TOAST pointer, producing either bogus value or crashing.

This is likely why the code was crashing on big-endian machines before
540f31680913 replaced the VARSIZE with VARSIZE_ANY, which however only
masked the issue.

Reported-by: Rushabh Lathia
Discussion: https://postgr.es/m/CAL-OGkthU9Gs7TZchf5OWaL-Gsi=hXqufTxKv9qpNG73d5na_g@mail.gmail.com

src/backend/access/common/detoast.c patch | blob | blame | history

diff --git a/src/backend/access/common/detoast.c b/src/backend/access/common/detoast.c

index f752ac7bbc917c1220eb764da6378a550d493b9d..8c89fc2a558bd6e199f92da55dec617fef9de403 100644 (file)

--- a/src/backend/access/common/detoast.c

+++ b/src/backend/access/common/detoast.c

@@ -233,7 +233,7 @@ detoast_attr_slice(struct varlena *attr,

* of a given length (after decompression).

max_size = pglz_maximum_compressed_size(sliceoffset + slicelength,

- TOAST_COMPRESS_SIZE(attr));

+ toast_pointer.va_extsize);

* Fetch enough compressed slices (compressed marker will get set

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