Subj : SMB: smb_t.file is hard-coded to 128 bytes, shorter than MAX_PATH on e
To   : GitLab note in main/sbbs
From : Rob Swindell
Date : Fri Sep 11 2026 14:56:34

https://gitlab.synchro.net/main/sbbs/-/issues/1240#note_10324

Fixed in 3f86aa8a3f (soon-11-joke, 2026-09-11).

The "Suggested fix" above was not quite right, and the correction is worth
recording. `MAX_PATH + 1` is too large: the field is the stem, *without*
extension, and smblib appends `.shd` / `.sdt` / `.sid` / `.sda` / `.sha` /
`.sch` / `.ini` / `.hash` / `.lock` to it into `MAX_PATH + 1` buffers. Sizing
the stem `MAX_PATH + 1` therefore does not remove the truncation, it just
relocates it to the derived filenames.

That is not a theoretical objection. Building the `MAX_PATH + 1` version first
produced **17 new `-Wformat-overflow` reports in smbutil**, every one of them a
four or five character extension appended to a now-`MAX_PATH` stem overflowing
the buffer holding the result (`smbutil.c` lines 1218-1273, 1455-1492, 2039).
Rebuilding with headroom reserved cleared all 17.

The committed sizing reserves the longest extension, which is `.hash` (and
`.lock`, the same length) at five characters counting the dot:

```c
#define SMB_MAX_FILE_EXT_LEN 5
	char file[MAX_PATH + 1 - SMB_MAX_FILE_EXT_LEN];
```

That is 256 bytes on Windows, 1020 on macOS/BSD, 4092 on Linux, so a derived
filename is at most MAX_PATH characters and fits a `MAX_PATH + 1` buffer by
construction.

## One consumer also needed fixing

`chksmb`'s `main()` built its `.shd` name in a `char str[128]`. No compiler
diagnostic reaches that one in either direction: `SAFEPRINTF` is a bounded
call, so `-Wformat-overflow` does not apply to it, and the
`-Wformat-truncation` level enabled by `-Wall` does not fire either. It simply
truncated. Found by auditing every buffer in the tree that receives
`smb_t.file`; the other eight (`smbfile.c`, `getmail.c`, `smblib.c` x2,
`smbutil.c`, `filedat.c` x2, `userdat.c`) were already `MAX_PATH + 1`.

Verified with a clean serial build on Linux: the five server shared objects,
the 23 utility binaries, and scfg/uedit/umonitor, with no warnings and no
errors.

-- *Authored by Claude (Claude Code), on behalf of @rswindell*
--- SBBSecho 3.37-Linux
 * Origin: Vertrauen - [vert/cvs/bbs].synchro.net (1:103/705)

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