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Fix user mount /dev/shm size 

Commit 7120976d74 ("Implement none, private, and shareable ipc
modes") introduces a bug: if a user-specified mount for /dev/shm
is provided, its size is overriden by value of ShmSize.

A reproducer is simple:

 docker run --rm
	--mount type=tmpfs,dst=/dev/shm,tmpfs-size=100K \
	alpine df /dev/shm

This commit is an attempt to fix the bug, as well as optimize things
a but and make the code easier to read.

https://github.com/moby/moby/issues/35271

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This commit is contained in:
Kir Kolyshkin 2017-10-27 00:21:41 -07:00
parent bbc4f78ba9
commit 31d30a985d
1 changed files with 21 additions and 17 deletions
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38
daemon/oci_linux.go
View File

@ -528,23 +528,35 @@ func setMounts(daemon *Daemon, s *specs.Spec, c *container.Container, mounts []c
userMounts[m.Destination] = struct{}{}
}
// Filter out mounts from spec
noIpc := c.HostConfig.IpcMode.IsNone()
// Filter out mounts that are overridden by user supplied mounts
// Copy all mounts from spec to defaultMounts, except for
// - mounts overriden by a user supplied mount;
// - all mounts under /dev if a user supplied /dev is present;
// - /dev/shm, in case IpcMode is none.
// While at it, also
// - set size for /dev/shm from shmsize.
var defaultMounts []specs.Mount
_, mountDev := userMounts["/dev"]
for _, m := range s.Mounts {
// filter out /dev/shm mount if case IpcMode is none
if noIpc && m.Destination == "/dev/shm" {
if _, ok := userMounts[m.Destination]; ok {
// filter out mount overridden by a user supplied mount
continue
}
// filter out mount overridden by a user supplied mount
if _, ok := userMounts[m.Destination]; !ok {
if mountDev && strings.HasPrefix(m.Destination, "/dev/") {
if mountDev && strings.HasPrefix(m.Destination, "/dev/") {
// filter out everything under /dev if /dev is user-mounted
continue
}
if m.Destination == "/dev/shm" {
if c.HostConfig.IpcMode.IsNone() {
// filter out /dev/shm for "none" IpcMode
continue
}
defaultMounts = append(defaultMounts, m)
// set size for /dev/shm mount from spec
sizeOpt := "size=" + strconv.FormatInt(c.HostConfig.ShmSize, 10)
m.Options = append(m.Options, sizeOpt)
}
defaultMounts = append(defaultMounts, m)
}
s.Mounts = defaultMounts
@ -652,14 +664,6 @@ func setMounts(daemon *Daemon, s *specs.Spec, c *container.Container, mounts []c
s.Linux.MaskedPaths = nil
}
// Set size for /dev/shm mount that comes from spec (IpcMode: private only)
for i, m := range s.Mounts {
if m.Destination == "/dev/shm" {
sizeOpt := "size=" + strconv.FormatInt(c.HostConfig.ShmSize, 10)
s.Mounts[i].Options = append(s.Mounts[i].Options, sizeOpt)
}
}
// TODO: until a kernel/mount solution exists for handling remount in a user namespace,
// we must clear the readonly flag for the cgroups mount (@mrunalp concurs)
if uidMap := daemon.idMappings.UIDs(); uidMap != nil || c.HostConfig.Privileged {