Bug: redbean: iterating unix.opendir can lead to random crashes with SIGSEGV SIGV_ACCERR #1337
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medium severity
Used to report medium severity bugs (e.g. Malfunctioning Features but still useable)
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andrei-markeev
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andrei-markeev
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I can't reproduce this. I need you to give me example code I can run with local function foo()
local dirInfo = assert(unix.opendir(dir or '.'))
for name, kind in dirInfo do
print(name)
end
end
foo()
collectgarbage("collect")Works fine. Same with explicit closes. I don't believe it's possible for // unix.Dir:close()
// ├─→ true
// └─→ nil, unix.Errno
static int LuaUnixDirClose(lua_State *L) {
DIR **dirp;
int rc, olderr;
dirp = GetUnixDirSelf(L);
if (*dirp) {
olderr = errno;
rc = closedir(*dirp);
*dirp = 0;
return SysretBool(L, "closedir", olderr, rc);
} else {
lua_pushboolean(L, true);
return 1;
}
} |
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I tried a couple of simple things and it is not easily reproducible indeed. In my original code, it was reproducing almost on every run. I will work towards a minimal example. It might take some time though because of Christmas. |
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Take your time. Please also check if this impacts redbean at head. You can build it as follows: |
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What happened?
Some time ago, I started getting random crashes with SIGSERV SIGV_ACCERR error. At first they weren't happening often, but then as I started doing more and more file system operations, they became very common (and very annoying 😅).
Crashes were occuring quite randomly, at different places, once I even had a crash that happened while server was idle.
One thing was common: the stack trace would always end with
LuaUnixDirCloseandclosedir.When dealing with file system, my typical approach is to crawl a directory recursively with
for name, kind in assert(unix.opendir(dir or '.')) do ... end, collecting a list of files into a table, and then do some operations with those files. For example, copy a bunch of files somewhere, concatenate them into one file, etc.Running with
--straceshowed that the crash was happening during garbage collection. A bunch of file descriptors were closed, last of them failing:(
munmapcalls skipped for brevity, full log attached below)After tracking file descriptors, I found that there were 2 descriptors pointing to the same folder:
Interestingly, those two
openatcalls belong to different requests and different API endpoints.I think this was what caused crashes - trying to close same fd twice.
I changed my code to explicitly close the
Dir, and crashes stopped.Version
redbean 3.0.0, also tried with a version from cosmo.zip from 12-Dec-2024
What operating system are you seeing the problem on?
Windows
Relevant log output
Full log doesn't fit, I had to attach it as a file: strace2_full.txt
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