Fix passing the value to EscapeChar.

[lonicerae]

• Properly handle the EscapeChar after refactor.

[rgerhards]

Please elaborate which problem is fixing this and how. uid_t at this places looks somewhat strange.

[lonicerae]

Hi @rgerhards !

Sorry for the rush.. Segfault call trace as follows:

Core was generated by `rsyslogd -n'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x000000000042f007 in setParserControlCharacterEscapePrefix (pVal=pVal@entry=0x0, pNewVal=0x2f <error: Cannot access memory at address 0x2f>) at glbl.c:524
524		loadConf->globals.parser.cCCEscapeChar = *pNewVal;
Missing separate debuginfos, use: dnf debuginfo-install libcap-2.48-5.fc37.x86_64 libestr-0.1.11-4.fc37.x86_64 libfastjson-0.99.9-4.fc37.x86_64 libgcc-12.3.1-1.fc37.x86_64 libuuid-2.38.1-1.fc37.x86_64 libzstd-1.5.5-1.fc37.x86_64 lz4-libs-1.9.4-1.fc37.x86_64 systemd-libs-251.19-1.fc37.x86_64 xz-libs-5.4.1-1.fc37.x86_64 zlib-1.2.12-5.fc37.x86_64
(gdb) bt
#0  0x000000000042f007 in setParserControlCharacterEscapePrefix (pVal=pVal@entry=0x0, pNewVal=0x2f <error: Cannot access memory at address 0x2f>) at glbl.c:524
#1  0x000000000046a256 in doGetChar (pp=0x7fff55bb7638, pSetHdlr=0x42f000 <setParserControlCharacterEscapePrefix>, pVal=0x0) at cfsysline.c:81
#2  0x000000000046b491 in cslchCallHdlr (ppConfLine=<optimized out>, pThis=<optimized out>) at cfsysline.c:782
#3  processCfSysLineCommand (pCmdName=pCmdName@entry=0x7fff55bb7690 "ControlCharacterEscapePrefix", p=p@entry=0x7fff55bb7688) at cfsysline.c:1022
#4  0x00000000004319cd in cfsysline (p=<optimized out>) at conf.c:239
#5  0x0000000000435a3b in cnfDoCfsysline (ln=0x125fcd0 "$ControlCharacterEscapePrefix /") at rsconf.c:628
#6  0x000000000042235d in yylex () at /home/shine/PROJ/rsyslog/grammar/lexer.l:434
#7  0x000000000041e58a in yyparse () at grammar.c:1408
#8  0x0000000000434e4d in load (cnf=0x4beee8 <ourConf>, confFile=0x47c74a "/etc/rsyslog.conf") at rsconf.c:1494
#9  0x000000000041105d in initAll (argc=argc@entry=2, argv=argv@entry=0x7fff55bb9728) at rsyslogd.c:1644
#10 0x000000000040f0ad in main (argc=2, argv=0x7fff55bb9728) at rsyslogd.c:2344
(gdb) f 1
#1  0x000000000046a256 in doGetChar (pp=0x7fff55bb7638, pSetHdlr=0x42f000 <setParserControlCharacterEscapePrefix>, pVal=0x0) at cfsysline.c:81
81				CHKiRet(pSetHdlr(pVal, **pp));
(gdb) p **pp
$1 = 47 '/'

I bisect the issue to commit 321fc76 . Seems it's a side effect after refactoring.

Relevant issue: #5376

[rgerhards]

do you have a sample conf that trigges the behavior?

[lonicerae]

Yes, the reproduction is easy. Just add this line to the /etc/rsyslog.conf:

$ControlCharacterEscapePrefix /

Or any char instead of the '/' can do.

The above call trace is from my Fedora + latest rsyslog.

Best regards,
Flos

[Cropi]

I see that in doGetChar, the handler function setParserControlCharacterEscapePrefix is called with the appropriate escape character, which is type of uchar. However, setParserControlCharacterEscapePrefix expects it to be uchar *, that's where the segfault happens.

I would rather use a different type than uid_t, as it's usually used to hold a used ID. Ideally a replacement could be uchar.