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authorIan Lewis <ianlewis@google.com>2019-11-26 18:19:47 -0800
committergVisor bot <gvisor-bot@google.com>2019-11-26 18:21:09 -0800
commit20279c305ece6a458006999c8dafc5672ca92803 (patch)
tree086e072c05f1bc0f6f1b972774fad452b7bb6c35 /pkg/sentry/syscalls
parent4a620c436dabbb0d5036e137bfdd44b945e3cff0 (diff)
Allow open(O_TRUNC) and (f)truncate for proc files.
This allows writable proc and devices files to be opened with O_CREAT|O_TRUNC. This is encountered most frequently when interacting with proc or devices files via the command line. e.g. $ echo 8192 1048576 4194304 > /proc/sys/net/ipv4/tcp_rmem Also adds a test to test the behavior of open(O_TRUNC), truncate, and ftruncate on named pipes. Fixes #1116 PiperOrigin-RevId: 282677425
Diffstat (limited to 'pkg/sentry/syscalls')
-rw-r--r--pkg/sentry/syscalls/linux/sys_file.go12
1 files changed, 10 insertions, 2 deletions
diff --git a/pkg/sentry/syscalls/linux/sys_file.go b/pkg/sentry/syscalls/linux/sys_file.go
index 167c2b60b..3b9181002 100644
--- a/pkg/sentry/syscalls/linux/sys_file.go
+++ b/pkg/sentry/syscalls/linux/sys_file.go
@@ -171,6 +171,9 @@ func openAt(t *kernel.Task, dirFD int32, addr usermem.Addr, flags uint) (fd uint
}
}
+ // Truncate is called when O_TRUNC is specified for any kind of
+ // existing Dirent. Behavior is delegated to the entry's Truncate
+ // implementation.
if flags&linux.O_TRUNC != 0 {
if err := d.Inode.Truncate(t, d, 0); err != nil {
return err
@@ -397,7 +400,9 @@ func createAt(t *kernel.Task, dirFD int32, addr usermem.Addr, flags uint, mode l
return err
}
- // Should we truncate the file?
+ // Truncate is called when O_TRUNC is specified for any kind of
+ // existing Dirent. Behavior is delegated to the entry's Truncate
+ // implementation.
if flags&linux.O_TRUNC != 0 {
if err := found.Inode.Truncate(t, found, 0); err != nil {
return err
@@ -1484,6 +1489,8 @@ func Truncate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
if fs.IsDir(d.Inode.StableAttr) {
return syserror.EISDIR
}
+ // In contrast to open(O_TRUNC), truncate(2) is only valid for file
+ // types.
if !fs.IsFile(d.Inode.StableAttr) {
return syserror.EINVAL
}
@@ -1522,7 +1529,8 @@ func Ftruncate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
return 0, nil, syserror.EINVAL
}
- // Note that this is different from truncate(2) above, where a
+ // In contrast to open(O_TRUNC), truncate(2) is only valid for file
+ // types. Note that this is different from truncate(2) above, where a
// directory returns EISDIR.
if !fs.IsFile(file.Dirent.Inode.StableAttr) {
return 0, nil, syserror.EINVAL