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Code Issues Releases Wiki Activity

um: separate child and parent errors in clone stub

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If the two are mixed up, then it looks as though the parent
returned an error if the child failed (before) the mmap(),
and then the resulting process never gets killed. Fix this
by splitting the child and parent errors, reporting and
using them appropriately.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Johannes Berg 2021-01-13 22:09:42 +01:00 committed by Richard Weinberger
parent a7d48886ca
commit 84b2789d61
5 changed files with 27 additions and 27 deletions
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2
arch/um/include/shared/skas/stub-data.h
View file

@ -11,7 +11,7 @@
struct stub_data {
unsigned long offset;
int fd;
long err;
long parent_err, child_err;
};
#endif

25
arch/um/kernel/skas/clone.c
View file

@ -24,29 +24,26 @@
void __attribute__ ((__section__ (".__syscall_stub")))
stub_clone_handler(void)
{
struct stub_data *data = (struct stub_data *) STUB_DATA;
int stack;
struct stub_data *data = (void *) ((unsigned long)&stack & ~(UM_KERN_PAGE_SIZE - 1));
long err;
err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD,
STUB_DATA + UM_KERN_PAGE_SIZE / 2 - sizeof(void *));
if (err != 0)
goto out;
(unsigned long)data + UM_KERN_PAGE_SIZE / 2 - sizeof(void *));
if (err) {
data->parent_err = err;
goto done;
}
err = stub_syscall4(__NR_ptrace, PTRACE_TRACEME, 0, 0, 0);
if (err)
goto out;
if (err) {
data->child_err = err;
goto done;
}
remap_stack(data->fd, data->offset);
goto done;
out:
/*
* save current result.
* Parent: pid;
* child: retcode of mmap already saved and it jumps around this
* assignment
*/
data->err = err;
done:
trap_myself();
}

23
arch/um/os-Linux/skas/process.c
View file

@ -545,8 +545,14 @@ int copy_context_skas0(unsigned long new_stack, int pid)
* and child's mmap2 calls
*/
*data = ((struct stub_data) {
.offset = MMAP_OFFSET(new_offset),
.fd = new_fd
.offset = MMAP_OFFSET(new_offset),
.fd = new_fd,
.parent_err = -ESRCH,
.child_err = 0,
});
*child_data = ((struct stub_data) {
.child_err = -ESRCH,
});
err = ptrace_setregs(pid, thread_regs);
@ -564,9 +570,6 @@ int copy_context_skas0(unsigned long new_stack, int pid)
return err;
}
/* set a well known return code for detection of child write failure */
child_data->err = 12345678;
/*
* Wait, until parent has finished its work: read child's pid from
* parent's stack, and check, if bad result.
@ -581,7 +584,7 @@ int copy_context_skas0(unsigned long new_stack, int pid)
wait_stub_done(pid);
pid = data->err;
pid = data->parent_err;
if (pid < 0) {
printk(UM_KERN_ERR "copy_context_skas0 - stub-parent reports "
"error %d\n", -pid);
@ -593,10 +596,10 @@ int copy_context_skas0(unsigned long new_stack, int pid)
* child's stack and check it.
*/
wait_stub_done(pid);
if (child_data->err != STUB_DATA) {
printk(UM_KERN_ERR "copy_context_skas0 - stub-child reports "
"error %ld\n", child_data->err);
err = child_data->err;
if (child_data->child_err != STUB_DATA) {
printk(UM_KERN_ERR "copy_context_skas0 - stub-child %d reports "
"error %ld\n", pid, data->child_err);
err = data->child_err;
goto out_kill;
}

2
arch/x86/um/shared/sysdep/stub_32.h
View file

@ -86,7 +86,7 @@ static inline void remap_stack(int fd, unsigned long offset)
"d" (PROT_READ | PROT_WRITE),
"S" (MAP_FIXED | MAP_SHARED), "D" (fd),
"a" (offset),
"i" (&((struct stub_data *) STUB_DATA)->err)
"i" (&((struct stub_data *) STUB_DATA)->child_err)
: "memory");
}

2
arch/x86/um/shared/sysdep/stub_64.h
View file

@ -92,7 +92,7 @@ static inline void remap_stack(long fd, unsigned long offset)
"d" (PROT_READ | PROT_WRITE),
"g" (MAP_FIXED | MAP_SHARED), "g" (fd),
"g" (offset),
"i" (&((struct stub_data *) STUB_DATA)->err)
"i" (&((struct stub_data *) STUB_DATA)->child_err)
: __syscall_clobber, "r10", "r8", "r9" );
}