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libdm: improve parallel create of control node

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When two parallel commands would have tried to create our
/dev/mapper/control node at the same time, one of them could
actually fail even if the 2nd. command actually mknod()
this control node correctly.

So for EEXIST case add detection if the control node is ok.

This may possibly help with some race case in early boot.
This commit is contained in:
Zdenek Kabelac 2023-02-12 23:44:43 +01:00
parent cf0dc9a13c
commit 7e14835a46
2 changed files with 14 additions and 4 deletions
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5
device_mapper/ioctl/libdm-iface.c
View File

@ -312,8 +312,13 @@ static int _create_control(const char *control, uint32_t major, uint32_t minor)
old_umask = umask(DM_CONTROL_NODE_UMASK); old_umask = umask(DM_CONTROL_NODE_UMASK);
if (mknod(control, S_IFCHR | S_IRUSR | S_IWUSR, if (mknod(control, S_IFCHR | S_IRUSR | S_IWUSR,
MKDEV(major, minor)) < 0) { MKDEV(major, minor)) < 0) {
if (errno != EEXIST) {
log_sys_error("mknod", control); log_sys_error("mknod", control);
ret = 0; ret = 0;
} else if (_control_exists(control, major, minor) != 1) {
stack; /* Invalid control node created by parallel command ? */
ret = 0;
}
} }
umask(old_umask); umask(old_umask);
(void) dm_prepare_selinux_context(NULL, 0); (void) dm_prepare_selinux_context(NULL, 0);

5
libdm/ioctl/libdm-iface.c
View File

@ -311,8 +311,13 @@ static int _create_control(const char *control, uint32_t major, uint32_t minor)
old_umask = umask(DM_CONTROL_NODE_UMASK); old_umask = umask(DM_CONTROL_NODE_UMASK);
if (mknod(control, S_IFCHR | S_IRUSR | S_IWUSR, if (mknod(control, S_IFCHR | S_IRUSR | S_IWUSR,
MKDEV(major, minor)) < 0) { MKDEV(major, minor)) < 0) {
if (errno != EEXIST) {
log_sys_error("mknod", control); log_sys_error("mknod", control);
ret = 0; ret = 0;
} else if (_control_exists(control, major, minor) != 1) {
stack; /* Invalid control node created by parallel command ? */
ret = 0;
}
} }
umask(old_umask); umask(old_umask);
(void) dm_prepare_selinux_context(NULL, 0); (void) dm_prepare_selinux_context(NULL, 0);