https://gitlab.synchro.net/main/sbbs/-/commit/eb01f9eed5d49a34d1bc76f2
Modified Files:
src/smblib/smballoc.c smblib.c src/smblib/tests/smballoctest.c
Log Message:
smblib: don't misallocate or truncate on a bad allocation file or read

Hazards in the allocation code that could overwrite or discard live
message headers or text:

- smb_allocdat() and smb_allochdr() treated a read error during the
scan for free blocks as the end of the allocation file, and so
allocated the new message at that point, on top of blocks in use.
A read error now fails the allocation. The scan loops predate the
2004 split of smblib.c.

- smb_freemsghdr() truncated the header file at the header being freed
whenever the header allocation file was not longer than that header's
end. A short or empty .sha (a missing one is created empty on open)
or a failed length query therefore discarded every later header. It
now truncates only when the header is exactly the last one accounted
for, and fails when the header lies beyond the allocation file.

- smb_freemsgdat() truncated the data file to the length implied by
the data allocation file. A failed length query yielded -1, which
divided to 0 and passed the ">= 0" check, truncating the data file to
nothing; a short .sda truncated text the same way. It now truncates
only the blocks it just removed from the end of the allocation file,
and only when the data file was no longer than that file accounted
for.

- smb_freemsgdat() left the .sda open, exclusively, on two early
returns when it had opened the file itself.

- smb_new_msghdr(), when moving an existing header that has outgrown
its blocks, unlocked a header lock held by its caller, so
smb_updatemsg() completed its index write unlocked. It now leaves a
caller-held lock in place in that case; smb_addmsghdr() still always
unlocks.

The truncation logic dates from 23523b22dfe (2017-11-16) and the
header-growth path from b18b0f6590c (2023-05-07).

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>

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