Fix SHMEM_ATTACH_UNKNOWN_SIZE when the shmem area doesn't exist
SHMEM_ATTACH_UNKNOWN_SIZE can be passed as argument to
ShmemRequestStruct() when the caller wants to attach to an existing
shared memory structure whose size it doesn't know. If the shared
memory structure doesn't exist, the request should fail, but instead,
ProcessShmemRequestsAfterStartup() tried to create the structure with
size = -1. That led to integer overflow in ShmemAllocRaw() and memory
corruption.
Fix by rejecting requests with SHMEM_ATTACH_UNKNOWN_SIZE when the
structure doesn't exist. Also add an integer overflow check in
ShmemAllocRaw(), to protect from this kind of confusion or simply too
large requests. Also document SHMEM_ATTACH_UNKNOWN_SIZE.
Author: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Discussion: https://www.postgresql.org/message-id/CAExHW5u_fTsOAS85kG981Vu6eR1GV-344rup6zYew7xMjEDREw@mail.gmail.com
Backpatch-through: 19
Branch
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master
Details
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https://git.postgresql.org/pg/commitdiff/311df1dc0392f06973cf98eac51d63cb007267ce
Modified Files
--------------
doc/src/sgml/xfunc.sgml | 10 ++++++++++
src/backend/storage/ipc/shmem.c | 22 ++++++++++++++++++++--
.../modules/test_shmem/t/001_late_shmem_alloc.pl | 17 +++++++++++++++++
src/test/modules/test_shmem/test_shmem.c | 11 +++++++----
4 files changed, 54 insertions(+), 6 deletions(-)
