Runtime Error in qstrdup: Null Pointer Returned from strdup Leading to Unexpected Behavior

[lobby-manager]

Description

When running the bgpd daemon, a runtime error is observed in lib/memory.c related to a null pointer being returned from a function that is expected to always return a valid pointer.

Version

commit 382e4e933

How to reproduce

1. Compile FRRouting with the following flag:
   export LDFLAGS="-L/root/protocols/rip/frr/libyang/build"
2. Configure the project:

./configure \
  --prefix=/usr \
  --sysconfdir=/etc \
  --localstatedir=/var \
  --enable-dev-build \
  --enable-user=frr \
  --enable-group=frr \
  --enable-vty-group=frrvty \
  --with-pkg-git-version \
  --with-pkg-extra-version=-my-manual-build \
  --enable-backtrace \
  --enable-rpki \
  --enable-mgmtd-test-be-client \
  --enable-sharpd \
  --enable-multipath=64 \
  --enable-snmp=agentx \
  --enable-irdp \
  --enable-snmp \
  --enable-static || exit 1

3. Compile the project:
   make -j$(nproc)
4. Start the zebra daemon:
   frr/zebra/zebra --limit-fds 100000 -d
5. Start bgpd:
   frr/bgpd/bgpd --limit-fds 100000 -p 179 -f /etc/bgpd.conf -i /var/run/frr/bgpd_1.pid --log stdout

Expected behavior

The qstrdup function should allocate memory for the input string using strdup and handle any errors gracefully, ensuring that mt_checkalloc only receives valid pointers.

Actual behavior

A runtime error is observed when qstrdup tries to duplicate a string:
lib/memory.c:118:63: runtime error: null pointer returned from function declared to never return null

Additional context

The issue seems to arise because qstrdup does not check if strdup returns NULL.

Checklist

• I have searched the open issues for this bug.
• I have not included sensitive information in this report.

[eqvinox]

Hm.

Our header says "passing NULL not allowed, never returns non-NULL":

frr/lib/memory.h

Lines 150 to 151 in 98ec22f

	extern void *qstrdup(struct memtype *mt, const char *str)
	__attribute__((malloc, nonnull(1) _RET_NONNULL));

which kinda contradicts the code "if NULL is passed, return NULL":

frr/lib/memory.c

Line 118 in 98ec22f

return str ? mt_checkalloc(mt, strdup(str), strlen(str) + 1) : NULL;

but really the question is… where are we calling this with a NULL string and should this be acceptable?

(I think [but have not confirmed] removing the _RET_NONNULL would be somewhat annoying too, as it might mislead all the compiler checks into thinking we need to check XSTRDUP return values…)