User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0

Steps to reproduce:

I had installed noscript and then started noticing these messages (see below). I restarted with all addons disabled and am seeing the same messages. This is a Linux Fedora Core 34 (x86_64)(Rawhide) system.

Messages:

Sandbox: unsupported flags 2048 in fstatat(-100, "/root/.config/gtk-3.0/colors.css", 0x7F3FD5414880, 2304)
Sandbox: seccomp sandbox violation: pid 160429, tid 163381, syscall 262, args 4294967196 139912163780352 139912137492608 2304 2304 1.
Sandbox: unsupported flags 2048 in fstatat(-100, "/root/.config/gtk-3.0/colors.css", 0x7F5C5221C880, 2304)
Sandbox: seccomp sandbox violation: pid 159820, tid 160011, syscall 262, args 4294967196 140034529416480 140034491664512 2304 2304 1.
Sandbox: unsupported flags 2048 in fstatat(-100, "/root/.config/gtk-3.0/colors.css", 0x7F02110D5880, 2304)
Sandbox: seccomp sandbox violation: pid 160069, tid 160215, syscall 262, args 4294967196 139646890351296 139646852749440 2304 2304 1.
Sandbox: unsupported flags 2048 in fstatat(-100, "/root/.config/gtk-3.0/colors.css", 0x7F3FD5414880, 2304)
Sandbox: seccomp sandbox violation: pid 160429, tid 163381, syscall 262, args 4294967196 139912163780352 139912137492608 2304 2304 1.
Sandbox: unsupported fd-relative fstatat(33, "", 0x7FFC9A5C3B40, 4096)
Sandbox: seccomp sandbox violation: pid 163373, tid 163373, syscall 262, args 33 140147465100138 140722898221888 4096 4096 1.
Sandbox: unsupported fd-relative fstatat(33, "", 0x7FFC9A5C3A30, 4096)
Sandbox: seccomp sandbox violation: pid 163373, tid 163373, syscall 262, args 33 140147465100138 140722898221616 4096 4096 1.
Sandbox: unsupported flags 2048 in fstatat(-100, "/root/.config/gtk-3.0/colors.css", 0x7F767FFD3880, 2304)
Sandbox: seccomp sandbox violation: pid 163373, tid 186756, syscall 262, args 4294967196 140146956872192 140146930169984 2304 2304 1.
Sandbox: unsupported flags 2048 in fstatat(-100, "/root/.config/gtk-3.0/colors.css", 0x7F5C5221C880, 2304)
Sandbox: seccomp sandbox violation: pid 159820, tid 160011, syscall 262, args 4294967196 140034529416480 140034491664512 2304 2304 1.
Sandbox: unsupported flags 2048 in fstatat(-100, "/root/.config/gtk-3.0/colors.css", 0x7F3FD5414880, 2304)
Sandbox: seccomp sandbox violation: pid 160429, tid 163381, syscall 262, args 4294967196 139912163780352 139912137492608 2304 2304 1.
Sandbox: unsupported flags 2048 in fstatat(-100, "/root/.config/gtk-3.0/colors.css", 0x7F02110D5880, 2304)

Actual results:

see above

Expected results:

No messages.

Info needed as to what one should do with these messages.

I could not reproduce this on the latest Nightly 84.0a1 and Ubuntu 20.04, I'm moving this to the Security: Process Sandboxing component so that someone with more knowledge in this area can take a look.

2048 is AT_NO_AUTOMOUNT; that should be fixed in D89121 / bug 1660901, which shipped yesterday in 82.0 and 78.4.

And unsupported fd-relative fstatat(33, "", …, 4096) is the AT_EMPTY_PATH issue, also fixed in bug 1660901.