Hi Shu-Chun, On 1/12/23 04:21, Shu-Chun Weng wrote:
Commit b8002058 strengthened openat()'s /proc detection by calling realpath(3) on the given path, which allows various paths and symlinks that points to the /proc file system to be intercepted correctly.Using realpath(3), though, has a side effect that it reads the symlinks along the way, and thus changes their atime. The results in the following code snippet already get ~now instead of the real atime: int fd = open("/path/to/a/symlink", O_PATH | O_NOFOLLOW); struct stat st; fstat(fd, st); return st.st_atime; This change opens a path that doesn't appear to be part of /proc directly and checks the destination of /proc/self/fd/n to determine if it actually refers to a file in /proc. Neither this nor the existing code works with symlinks or indirect paths (e.g. /tmp/../proc/self/exe) that points to /proc/self/exe because it is itself a symlink, and both realpath(3) and /proc/self/fd/n will resolve into the location of QEMU.
Does this fix any of the following issues? https://gitlab.com/qemu-project/qemu/-/issues/829 https://gitlab.com/qemu-project/qemu/-/issues/927 https://gitlab.com/qemu-project/qemu/-/issues/2004
Signed-off-by: Shu-Chun Weng <s...@google.com> --- linux-user/syscall.c | 42 +++++++++++++++++++++++++++++++++--------- 1 file changed, 33 insertions(+), 9 deletions(-)
