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linux-user: Fix openat() emulation to correctly detect accesses to /proc 

In qemu we catch accesses to files like /proc/cpuinfo or /proc/net/route
and return to the guest contents which would be visible on a real system
(instead what the host would show).

This patch fixes a bug, where for example the accesses
    cat /proc////cpuinfo
or
    cd /proc && cat cpuinfo
will not be recognized by qemu and where qemu will wrongly show
the contents of the host's /proc/cpuinfo file.

Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20230803214450.647040-2-deller@gmx.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Helge Deller 2023-08-03 23:44:47 +02:00 committed by Richard Henderson
parent 47d1e98231
commit b8002058c4
1 changed files with 12 additions and 1 deletions
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13
linux-user/syscall.c
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@ -8557,9 +8557,12 @@ static int open_hardware(CPUArchState *cpu_env, int fd)
}
#endif
int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *pathname,
int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *fname,
int flags, mode_t mode, bool safe)
{
g_autofree char *proc_name = NULL;
const char *pathname;
struct fake_open {
const char *filename;
int (*fill)(CPUArchState *cpu_env, int fd);
@ -8585,6 +8588,14 @@ int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *pathname,
{ NULL, NULL, NULL }
};
/* if this is a file from /proc/ filesystem, expand full name */
proc_name = realpath(fname, NULL);
if (proc_name && strncmp(proc_name, "/proc/", 6) == 0) {
pathname = proc_name;
} else {
pathname = fname;
}
if (is_proc_myself(pathname, "exe")) {
if (safe) {
return safe_openat(dirfd, exec_path, flags, mode);