Useful for
* limiting privileges
* opening block devices O_EXCL
Use dup to work around the fact /proc/self/fd
can't be opened after dropping privileges.
This proc behaviour doesn't match TLPI and might be a bug.
Qemu has a slightly more complex fdset approach
that provides fds with different access permissions.
Signed-off-by: Gabriel de Perthuis <g2p.c...@gmail.com>
---
arch/um/os-Linux/file.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c
index c17bd6f..cee65ba 100644
--- a/arch/um/os-Linux/file.c
+++ b/arch/um/os-Linux/file.c
@@ -169,11 +169,11 @@ int os_file_mode(const char *file, struct openflags
*mode_out)
return err;
}
int os_open_file(const char *file, struct openflags flags, int mode)
{
- int fd, err, f = 0;
+ int fd, fd0, err, f = 0;
if (flags.r && flags.w)
f = O_RDWR;
else if (flags.r)
f = O_RDONLY;
@@ -190,11 +190,15 @@ int os_open_file(const char *file, struct openflags
flags, int mode)
if (flags.e)
f |= O_EXCL;
if (flags.a)
f |= O_APPEND;
- fd = open64(file, f, mode);
+ if (!strncmp(file, "/dev/fd/", 8)
+ && sscanf(file, "/dev/fd/%d", &fd0) == 1)
+ fd = dup(fd0);
+ else
+ fd = open64(file, f, mode);
if (fd < 0)
return -errno;
if (flags.cl && fcntl(fd, F_SETFD, 1)) {
err = -errno;
@@ -280,11 +284,11 @@ int os_file_size(const char *file, unsigned long long
*size_out)
if (S_ISBLK(buf.ust_mode)) {
int fd;
long blocks;
- fd = open(file, O_RDONLY, 0);
+ fd = os_open_file(file, of_read(OPENFLAGS()), 0);
if (fd < 0) {
err = -errno;
printk(UM_KERN_ERR "Couldn't open \"%s\", "
"errno = %d\n", file, errno);
return err;
--
1.8.3.3.758.g90e98ff
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