Before commit 44f73c5a62 ("Cygwin: Fix segfalt when too many command
line args are specified.") we had no actual argument size limit, except
for the fact that the child process created another copy of the argv
array on the stack, which could result in a stack overflow and a
subsequent SEGV. Commit 44f73c5a62 changed that by allocating the
additional argv array via malloc, and it introduced a new SC_ARG_MAX
limit along the lines of the typical Linux limit.
However, this new limit is artificial. Cygwin allocates all argument
and environment data on the cygheap. We only run out of ARG_MAX space
if we're out of memory resources.
Change argument size handling accordingly:
- Drop the args size check from child_info_spawn::worker.
- Return -1 from sysconf (SC_ARG_MAX), i. e., the argument size limit
is undefined.
- Change argv handling in class av, so that a failing cmalloc is not
fatal. This allows the parent process to return E2BIG if it's out
of cygheap resources.
- In the child, add a check around the new malloc call, so that it
doesn't result in a SEGV if the child process gets unexpectedly into
an ENOMEM situation at this point. In this (unlikely) case, proceed
with the original __argv array instead. Add comment to explain why.
Fixes: 44f73c5a62 ("Cygwin: Fix segfalt when too many command line args are specified.")
Tested-by: Takashi Yano <takashi.yano@nifty.ne.jp>
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Previously, the number of command line args was not checked for
cygwin process. Due to this, segmentation fault was caused if too
many command line args are specified.
https://cygwin.com/pipermail/cygwin/2023-August/254333.html
Since char *argv[argc + 1] is placed on the stack in dll_crt0_1(),
STATUS_STACK_OVERFLOW occurs if the stack does not have enough
space.
With this patch, char *argv[] is placed in heap instead of stack
and ARG_MAX is increased from 32000 to 2097152 which is default
value of Linux. The argument length is also compared with ARG_MAX
and spawnve() returns E2BIG if it is too long.
Reported-by: Ed Morton
Reviewed-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
Previously, the console device could not be accessed from other terminals.
Due to this limitation, GNU screen and tmux cannot be opened in console.
With this patch, console device can be accessed from other TTYs, such as
other consoles or ptys. Thanks to this patch, screen and tmux get working
in console.
Reviewed-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
Corinna Vinschen
Takashi Yano