Bad address error on Linux write syscall on RHEL 9.4 => fixed in svn

[scampbell]

I have a shared folder (shared from Windows 11 host to RHEL 9.4 guest) that is mounted as filesystem type vboxsf:

VM_Share on /mnt/vm_share type vboxsf (rw,nodev,relatime,iocharset=utf8,uid=0,gid=1000,dmode=0770,fmode=0770,tag=VBoxAutomounter)

While attempting to perform Native AOT compilation of a .NET project located on this shared folder from the Linux guest, I started receiving errors when attempting to write the executable to disk. Using strace, I narrowed this down to a write() syscall that is larger than a certain size. I wrote a test program in C to eliminate anything other than this syscall.

#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>

#define ONE_MB_BYTES 1048576

int do_write(char * filename, int num_bytes) {
	printf("Going to test %s\n", filename);

	int fd = open(filename, O_CREAT | O_WRONLY );
	if (fd == -1) {
		printf("\tCould not create/open file: errno %d - %s\n", errno, strerror(errno));
		return 1;
	}
	char *buffer = (char *)malloc(num_bytes);
	if(buffer == NULL) {
		printf("\tCould not malloc buffer sz: %d\n", num_bytes);
		return 4;
	}
	memset(buffer, 'A', num_bytes);
	buffer[num_bytes-1] = '\0';
	size_t written_bytes = write(fd, buffer, num_bytes);
	free(buffer);

	if (written_bytes == -1) {
		printf("\tError writing text: errno %d - %s\n", errno, strerror(errno));
		if(close(fd) == -1) {
			printf("\tError closing file: errno %d - %s\n", errno, strerror(errno));
		}
		return 2;
	}
	else if (written_bytes < num_bytes) {
		printf("\tWarning: Only %d of %d bytes written.\n", written_bytes, num_bytes);
	}

	if(close(fd) == -1) {
		printf("\tError closing file: errno %d - %s\n", errno, strerror(errno));
		return 3;
	}
	printf("\tTEST %s PASSED\n", filename);
	return 0;
}

int main(int argc, char ** argv) {
	do_write("test_1mb.txt", 1*ONE_MB_BYTES);
	do_write("test_2mb.txt", 2*ONE_MB_BYTES);
	do_write("test_4mb.txt", 4*ONE_MB_BYTES);
	do_write("test_5mb.txt", 5*ONE_MB_BYTES);
	do_write("test_6mb.txt", 6*ONE_MB_BYTES);
	do_write("test_7mb.txt", 7*ONE_MB_BYTES);
	do_write("test_8mb.txt", 8*ONE_MB_BYTES);
	do_write("test_16mb.txt", 16*ONE_MB_BYTES);
	do_write("test_32mb.txt", 32*ONE_MB_BYTES);
	do_write("test_64mb.txt", 64*ONE_MB_BYTES);
	return 0;
}

With this test program, the writes of size 8 MB and larger fail:

Going to test test_1mb.txt
	TEST test_1mb.txt PASSED
Going to test test_2mb.txt
	TEST test_2mb.txt PASSED
Going to test test_4mb.txt
	TEST test_4mb.txt PASSED
Going to test test_5mb.txt
	TEST test_5mb.txt PASSED
Going to test test_6mb.txt
	TEST test_6mb.txt PASSED
Going to test test_7mb.txt
	TEST test_7mb.txt PASSED
Going to test test_8mb.txt
	Error writing text: errno 14 - Bad address
Going to test test_16mb.txt
	Error writing text: errno 14 - Bad address
Going to test test_32mb.txt
	Error writing text: errno 14 - Bad address
Going to test test_64mb.txt
	Error writing text: errno 14 - Bad address

Relevant strace output:

write(1, "Going to test test_8mb.txt\n", 27Going to test test_8mb.txt
) = 27
openat(AT_FDCWD, "test_8mb.txt", O_WRONLY|O_CREAT, 000) = 3
mmap(NULL, 8392704, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb7ee1ff000
write(3, "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"..., 8388608) = -1 EFAULT (Bad address)
munmap(0x7fb7ee1ff000, 8392704)         = 0
write(1, "\tError writing text: errno 14 - "..., 44	Error writing text: errno 14 - Bad address
) = 44
close(3)  

I found ticket #22165, which appears very similar, so I attempted similar troubleshooting steps.

• This only occurs on vboxsf shared folders. A pure Linux xfs file system on the Linux guest did not reproduce this.
• Smaller writes do not exhibit this issue, only above a certain size (see output from test program above)
• This does not reproduce with RHEL 9.2 or RHEL 9.3. All writes from 1 to 64 MB execute successfully on those kernels. (RHEL 9.2 kernel is 5.14.0-284.11.1.el9_2.x86_64. RHEL 9.3 kernel is 5.14.0-362.8.1.el9_3.x86_64. RHEL 9.4 kernel is 5.14.0-427.13.1.el9_4.x86_64)
• This was also reproduceable with VirtualBox 6.1.50 and Guest Additions 6.1.50 with RHEL 9.4.

[galitsyn]

Hi scampbell,

Please attach VBox.log. I gave it a quick try with few Linux guests and do not see the issue on Linux host when running attached POC. I will give it a try with Windows host later on, but maybe VBox.log can shed more light already now.

UPD: Managed to reproduce w/ CentOS Stream 9 (5.14.0-547.el9.x86_64) guest on Linux host as well.

[scampbell]

Hi galitsyn,

Please let me know if you would still like the VBox.log since you were able to reproduce. Thanks.

[scampbell]

Issue persists with VirtualBox 7.1.6 and Guest Additions 7.1.6

[galitsyn]

Hi scampbell,

The issue now should be fixed. If you would like to give it a try, please pick up one of Guest Additions builds from test builds page. Thank you for reporting the issue and providing POC to reproduce it.

[scampbell]

Hi galitsyn,

I tried Guest Additions testbuild 167673 and was able to complete all writes successfully, and tested my original issue to stumble upon this, and that completed successfully as well. Thank you for resolving this issue so quickly!

[Guillermo Jano]

Seemingly this also fixes #22165, tested with 7.1.7r167766 and Rocky Linux kernel 5.14.0-503.26.1.el9_5.x86_64