[PATCH 10/10] mm: replace access_process_vm() write parameter with gup_flags

Lorenzo Stoakes
2016-10-13T00:20:20Z

This patch removes the write parameter from access_process_vm() and replaces it
with a gup_flags parameter as use of this function previously _implied_
FOLL_FORCE, whereas after this patch callers explicitly pass this flag.

We make this explicit as use of FOLL_FORCE can result in surprising behaviour
(and hence bugs) within the mm subsystem.

Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
---
arch/alpha/kernel/ptrace.c | 9 ++++++---
arch/blackfin/kernel/ptrace.c | 5 +++--
arch/cris/arch-v32/kernel/ptrace.c | 4 ++--
arch/ia64/kernel/ptrace.c | 14 +++++++++-----
arch/m32r/kernel/ptrace.c | 15 ++++++++++-----
arch/mips/kernel/ptrace32.c | 5 +++--
arch/powerpc/kernel/ptrace32.c | 5 +++--
arch/score/kernel/ptrace.c | 10 ++++++----
arch/sparc/kernel/ptrace_64.c | 24 ++++++++++++++++--------
arch/x86/kernel/step.c | 3 ++-
arch/x86/um/ptrace_32.c | 3 ++-
arch/x86/um/ptrace_64.c | 3 ++-
include/linux/mm.h | 3 ++-
kernel/ptrace.c | 16 ++++++++++------
mm/memory.c | 8 ++------
mm/nommu.c | 6 +++---
mm/util.c | 5 +++--
17 files changed, 84 insertions(+), 54 deletions(-)

diff --git a/arch/alpha/kernel/ptrace.c b/arch/alpha/kernel/ptrace.c
index d9ee817..940dfb4 100644
--- a/arch/alpha/kernel/ptrace.c
+++ b/arch/alpha/kernel/ptrace.c
@@ -157,14 +157,16 @@ put_reg(struct task_struct *task, unsigned long regno, unsigned long data)
static inline int
read_int(struct task_struct *task, unsigned long addr, int * data)
{
- int copied = access_process_vm(task, addr, data, sizeof(int), 0);
+ int copied = access_process_vm(task, addr, data, sizeof(int),
+ FOLL_FORCE);
return (copied == sizeof(int)) ? 0 : -EIO;
}

static inline int
write_int(struct task_struct *task, unsigned long addr, int data)
{
- int copied = access_process_vm(task, addr, &data, sizeof(int), 1);
+ int copied = access_process_vm(task, addr, &data, sizeof(int),
+ FOLL_FORCE | FOLL_WRITE);
return (copied == sizeof(int)) ? 0 : -EIO;
}

@@ -281,7 +283,8 @@ long arch_ptrace(struct task_struct *child, long request,
/* When I and D space are separate, these will need to be fixed. */
case PTRACE_PEEKTEXT: /* read word at location addr. */
case PTRACE_PEEKDATA:
- copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
+ copied = access_process_vm(child, addr, &tmp, sizeof(tmp),
+ FOLL_FORCE);
ret = -EIO;
if (copied != sizeof(tmp))
break;
diff --git a/arch/blackfin/kernel/ptrace.c b/arch/blackfin/kernel/ptrace.c
index 8b8fe67..8d79286 100644
--- a/arch/blackfin/kernel/ptrace.c
+++ b/arch/blackfin/kernel/ptrace.c
@@ -271,7 +271,7 @@ long arch_ptrace(struct task_struct *child, long request,
case BFIN_MEM_ACCESS_CORE:
case BFIN_MEM_ACCESS_CORE_ONLY:
copied = access_process_vm(child, addr, &tmp,
- to_copy, 0);
+ to_copy, FOLL_FORCE);
if (copied)
break;

@@ -324,7 +324,8 @@ long arch_ptrace(struct task_struct *child, long request,
case BFIN_MEM_ACCESS_CORE:
case BFIN_MEM_ACCESS_CORE_ONLY:
copied = access_process_vm(child, addr, &data,
- to_copy, 1);
+ to_copy,
+ FOLL_FORCE | FOLL_WRITE);
break;
case BFIN_MEM_ACCESS_DMA:
if (safe_dma_memcpy(paddr, &data, to_copy))
diff --git a/arch/cris/arch-v32/kernel/ptrace.c b/arch/cris/arch-v32/kernel/ptrace.c
index f085229..f0df654 100644
--- a/arch/cris/arch-v32/kernel/ptrace.c
+++ b/arch/cris/arch-v32/kernel/ptrace.c
@@ -147,7 +147,7 @@ long arch_ptrace(struct task_struct *child, long request,
/* The trampoline page is globally mapped, no page table to traverse.*/
tmp = *(unsigned long*)addr;
} else {
- copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
+ copied = access_process_vm(child, addr, &tmp, sizeof(tmp), FOLL_FORCE);

if (copied != sizeof(tmp))
break;
@@ -279,7 +279,7 @@ static int insn_size(struct task_struct *child, unsigned long pc)
int opsize = 0;

/* Read the opcode at pc (do what PTRACE_PEEKTEXT would do). */
- copied = access_process_vm(child, pc, &opcode, sizeof(opcode), 0);
+ copied = access_process_vm(child, pc, &opcode, sizeof(opcode), FOLL_FORCE);
if (copied != sizeof(opcode))
return 0;

diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c
index 6f54d51..31aa8c0 100644
--- a/arch/ia64/kernel/ptrace.c
+++ b/arch/ia64/kernel/ptrace.c
@@ -453,7 +453,7 @@ ia64_peek (struct task_struct *child, struct switch_stack *child_stack,
return 0;
}
}
- copied = access_process_vm(child, addr, &ret, sizeof(ret), 0);
+ copied = access_process_vm(child, addr, &ret, sizeof(ret), FOLL_FORCE);
if (copied != sizeof(ret))
return -EIO;
*val = ret;
@@ -489,7 +489,8 @@ ia64_poke (struct task_struct *child, struct switch_stack *child_stack,
*ia64_rse_skip_regs(krbs, regnum) = val;
}
}
- } else if (access_process_vm(child, addr, &val, sizeof(val), 1)
+ } else if (access_process_vm(child, addr, &val, sizeof(val),
+ FOLL_FORCE | FOLL_WRITE)
!= sizeof(val))
return -EIO;
return 0;
@@ -543,7 +544,8 @@ ia64_sync_user_rbs (struct task_struct *child, struct switch_stack *sw,
ret = ia64_peek(child, sw, user_rbs_end, addr, &val);
if (ret < 0)
return ret;
- if (access_process_vm(child, addr, &val, sizeof(val), 1)
+ if (access_process_vm(child, addr, &val, sizeof(val),
+ FOLL_FORCE | FOLL_WRITE)
!= sizeof(val))
return -EIO;
}
@@ -559,7 +561,8 @@ ia64_sync_kernel_rbs (struct task_struct *child, struct switch_stack *sw,

/* now copy word for word from user rbs to kernel rbs: */
for (addr = user_rbs_start; addr < user_rbs_end; addr += 8) {
- if (access_process_vm(child, addr, &val, sizeof(val), 0)
+ if (access_process_vm(child, addr, &val, sizeof(val),
+ FOLL_FORCE)
!= sizeof(val))
return -EIO;

@@ -1156,7 +1159,8 @@ arch_ptrace (struct task_struct *child, long request,
case PTRACE_PEEKTEXT:
case PTRACE_PEEKDATA:
/* read word at location addr */
- if (access_process_vm(child, addr, &data, sizeof(data), 0)
+ if (access_process_vm(child, addr, &data, sizeof(data),
+ FOLL_FORCE)
!= sizeof(data))
return -EIO;
/* ensure return value is not mistaken for error code */
diff --git a/arch/m32r/kernel/ptrace.c b/arch/m32r/kernel/ptrace.c
index 51f5e9a..c145605 100644
--- a/arch/m32r/kernel/ptrace.c
+++ b/arch/m32r/kernel/ptrace.c
@@ -493,7 +493,8 @@ unregister_all_debug_traps(struct task_struct *child)
int i;

for (i = 0; i < p->nr_trap; i++)
- access_process_vm(child, p->addr[i], &p->insn[i], sizeof(p->insn[i]), 1);
+ access_process_vm(child, p->addr[i], &p->insn[i], sizeof(p->insn[i]),
+ FOLL_FORCE | FOLL_WRITE);
p->nr_trap = 0;
}

@@ -537,7 +538,8 @@ embed_debug_trap(struct task_struct *child, unsigned long next_pc)
unsigned long next_insn, code;
unsigned long addr = next_pc & ~3;

- if (access_process_vm(child, addr, &next_insn, sizeof(next_insn), 0)
+ if (access_process_vm(child, addr, &next_insn, sizeof(next_insn),
+ FOLL_FORCE)
!= sizeof(next_insn)) {
return -1; /* error */
}
@@ -546,7 +548,8 @@ embed_debug_trap(struct task_struct *child, unsigned long next_pc)
if (register_debug_trap(child, next_pc, next_insn, &code)) {
return -1; /* error */
}
- if (access_process_vm(child, addr, &code, sizeof(code), 1)
+ if (access_process_vm(child, addr, &code, sizeof(code),
+ FOLL_FORCE | FOLL_WRITE)
!= sizeof(code)) {
return -1; /* error */
}
@@ -562,7 +565,8 @@ withdraw_debug_trap(struct pt_regs *regs)
addr = (regs->bpc - 2) & ~3;
regs->bpc -= 2;
if (unregister_debug_trap(current, addr, &code)) {
- access_process_vm(current, addr, &code, sizeof(code), 1);
+ access_process_vm(current, addr, &code, sizeof(code),
+ FOLL_FORCE | FOLL_WRITE);
invalidate_cache();
}
}
@@ -589,7 +593,8 @@ void user_enable_single_step(struct task_struct *child)
/* Compute next pc. */
pc = get_stack_long(child, PT_BPC);

- if (access_process_vm(child, pc&~3, &insn, sizeof(insn), 0)
+ if (access_process_vm(child, pc&~3, &insn, sizeof(insn),
+ FOLL_FORCE)
!= sizeof(insn))
return;

diff --git a/arch/mips/kernel/ptrace32.c b/arch/mips/kernel/ptrace32.c
index 283b5a1..7e71a4e 100644
--- a/arch/mips/kernel/ptrace32.c
+++ b/arch/mips/kernel/ptrace32.c
@@ -70,7 +70,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
break;

copied = access_process_vm(child, (u64)addrOthers, &tmp,
- sizeof(tmp), 0);
+ sizeof(tmp), FOLL_FORCE);
if (copied != sizeof(tmp))
break;
ret = put_user(tmp, (u32 __user *) (unsigned long) data);
@@ -179,7 +179,8 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
break;
ret = 0;
if (access_process_vm(child, (u64)addrOthers, &data,
- sizeof(data), 1) == sizeof(data))
+ sizeof(data),
+ FOLL_FORCE | FOLL_WRITE) == sizeof(data))
break;
ret = -EIO;
break;
diff --git a/arch/powerpc/kernel/ptrace32.c b/arch/powerpc/kernel/ptrace32.c
index f52b7db3..010b7b3 100644
--- a/arch/powerpc/kernel/ptrace32.c
+++ b/arch/powerpc/kernel/ptrace32.c
@@ -74,7 +74,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
break;

copied = access_process_vm(child, (u64)addrOthers, &tmp,
- sizeof(tmp), 0);
+ sizeof(tmp), FOLL_FORCE);
if (copied != sizeof(tmp))
break;
ret = put_user(tmp, (u32 __user *)data);
@@ -179,7 +179,8 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
break;
ret = 0;
if (access_process_vm(child, (u64)addrOthers, &tmp,
- sizeof(tmp), 1) == sizeof(tmp))
+ sizeof(tmp),
+ FOLL_FORCE | FOLL_WRITE) == sizeof(tmp))
break;
ret = -EIO;
break;
diff --git a/arch/score/kernel/ptrace.c b/arch/score/kernel/ptrace.c
index 5583618..4f7314d 100644
--- a/arch/score/kernel/ptrace.c
+++ b/arch/score/kernel/ptrace.c
@@ -131,7 +131,7 @@ read_tsk_long(struct task_struct *child,
{
int copied;

- copied = access_process_vm(child, addr, res, sizeof(*res), 0);
+ copied = access_process_vm(child, addr, res, sizeof(*res), FOLL_FORCE);

return copied != sizeof(*res) ? -EIO : 0;
}
@@ -142,7 +142,7 @@ read_tsk_short(struct task_struct *child,
{
int copied;

- copied = access_process_vm(child, addr, res, sizeof(*res), 0);
+ copied = access_process_vm(child, addr, res, sizeof(*res), FOLL_FORCE);

return copied != sizeof(*res) ? -EIO : 0;
}
@@ -153,7 +153,8 @@ write_tsk_short(struct task_struct *child,
{
int copied;

- copied = access_process_vm(child, addr, &val, sizeof(val), 1);
+ copied = access_process_vm(child, addr, &val, sizeof(val),
+ FOLL_FORCE | FOLL_WRITE);

return copied != sizeof(val) ? -EIO : 0;
}
@@ -164,7 +165,8 @@ write_tsk_long(struct task_struct *child,
{
int copied;

- copied = access_process_vm(child, addr, &val, sizeof(val), 1);
+ copied = access_process_vm(child, addr, &val, sizeof(val),
+ FOLL_FORCE | FOLL_WRITE);

return copied != sizeof(val) ? -EIO : 0;
}
diff --git a/arch/sparc/kernel/ptrace_64.c b/arch/sparc/kernel/ptrace_64.c
index 9ddc492..ac082dd 100644
--- a/arch/sparc/kernel/ptrace_64.c
+++ b/arch/sparc/kernel/ptrace_64.c
@@ -127,7 +127,8 @@ static int get_from_target(struct task_struct *target, unsigned long uaddr,
if (copy_from_user(kbuf, (void __user *) uaddr, len))
return -EFAULT;
} else {
- int len2 = access_process_vm(target, uaddr, kbuf, len, 0);
+ int len2 = access_process_vm(target, uaddr, kbuf, len,
+ FOLL_FORCE);
if (len2 != len)
return -EFAULT;
}
@@ -141,7 +142,8 @@ static int set_to_target(struct task_struct *target, unsigned long uaddr,
if (copy_to_user((void __user *) uaddr, kbuf, len))
return -EFAULT;
} else {
- int len2 = access_process_vm(target, uaddr, kbuf, len, 1);
+ int len2 = access_process_vm(target, uaddr, kbuf, len,
+ FOLL_FORCE | FOLL_WRITE);
if (len2 != len)
return -EFAULT;
}
@@ -505,7 +507,8 @@ static int genregs32_get(struct task_struct *target,
if (access_process_vm(target,
(unsigned long)
&reg_window[pos],
- k, sizeof(*k), 0)
+ k, sizeof(*k),
+ FOLL_FORCE)
!= sizeof(*k))
return -EFAULT;
k++;
@@ -531,12 +534,14 @@ static int genregs32_get(struct task_struct *target,
if (access_process_vm(target,
(unsigned long)
&reg_window[pos],
- &reg, sizeof(reg), 0)
+ &reg, sizeof(reg),
+ FOLL_FORCE)
!= sizeof(reg))
return -EFAULT;
if (access_process_vm(target,
(unsigned long) u,
- &reg, sizeof(reg), 1)
+ &reg, sizeof(reg),
+ FOLL_FORCE | FOLL_WRITE)
!= sizeof(reg))
return -EFAULT;
pos++;
@@ -615,7 +620,8 @@ static int genregs32_set(struct task_struct *target,
(unsigned long)
&reg_window[pos],
(void *) k,
- sizeof(*k), 1)
+ sizeof(*k),
+ FOLL_FORCE | FOLL_WRITE)
!= sizeof(*k))
return -EFAULT;
k++;
@@ -642,13 +648,15 @@ static int genregs32_set(struct task_struct *target,
if (access_process_vm(target,
(unsigned long)
u,
- &reg, sizeof(reg), 0)
+ &reg, sizeof(reg),
+ FOLL_FORCE)
!= sizeof(reg))
return -EFAULT;
if (access_process_vm(target,
(unsigned long)
&reg_window[pos],
- &reg, sizeof(reg), 1)
+ &reg, sizeof(reg),
+ FOLL_FORCE | FOLL_WRITE)
!= sizeof(reg))
return -EFAULT;
pos++;
diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
index c9a0738..a23ce84 100644
--- a/arch/x86/kernel/step.c
+++ b/arch/x86/kernel/step.c
@@ -57,7 +57,8 @@ static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
unsigned char opcode[15];
unsigned long addr = convert_ip_to_linear(child, regs);

- copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
+ copied = access_process_vm(child, addr, opcode, sizeof(opcode),
+ FOLL_FORCE);
for (i = 0; i < copied; i++) {
switch (opcode[i]) {
/* popf and iret */
diff --git a/arch/x86/um/ptrace_32.c b/arch/x86/um/ptrace_32.c
index 5766ead..60a5a5a 100644
--- a/arch/x86/um/ptrace_32.c
+++ b/arch/x86/um/ptrace_32.c
@@ -36,7 +36,8 @@ int is_syscall(unsigned long addr)
* slow, but that doesn't matter, since it will be called only
* in case of singlestepping, if copy_from_user failed.
*/
- n = access_process_vm(current, addr, &instr, sizeof(instr), 0);
+ n = access_process_vm(current, addr, &instr, sizeof(instr),
+ FOLL_FORCE);
if (n != sizeof(instr)) {
printk(KERN_ERR "is_syscall : failed to read "
"instruction from 0x%lx\n", addr);
diff --git a/arch/x86/um/ptrace_64.c b/arch/x86/um/ptrace_64.c
index 0b5c184..e30202b 100644
--- a/arch/x86/um/ptrace_64.c
+++ b/arch/x86/um/ptrace_64.c
@@ -212,7 +212,8 @@ int is_syscall(unsigned long addr)
* slow, but that doesn't matter, since it will be called only
* in case of singlestepping, if copy_from_user failed.
*/
- n = access_process_vm(current, addr, &instr, sizeof(instr), 0);
+ n = access_process_vm(current, addr, &instr, sizeof(instr),
+ FOLL_FORCE);
if (n != sizeof(instr)) {
printk("is_syscall : failed to read instruction from "
"0x%lx\n", addr);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 3e5234e..7beda79 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1266,7 +1266,8 @@ static inline int fixup_user_fault(struct task_struct *tsk,
}
#endif

-extern int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write);
+extern int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len,
+ unsigned int gup_flags);
extern int access_remote_vm(struct mm_struct *mm, unsigned long addr,
void *buf, int len, unsigned int gup_flags);

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 2a99027..e6474f7 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -537,7 +537,7 @@ int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst
int this_len, retval;

this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
- retval = access_process_vm(tsk, src, buf, this_len, 0);
+ retval = access_process_vm(tsk, src, buf, this_len, FOLL_FORCE);
if (!retval) {
if (copied)
break;
@@ -564,7 +564,8 @@ int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long ds
this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
if (copy_from_user(buf, src, this_len))
return -EFAULT;
- retval = access_process_vm(tsk, dst, buf, this_len, 1);
+ retval = access_process_vm(tsk, dst, buf, this_len,
+ FOLL_FORCE | FOLL_WRITE);
if (!retval) {
if (copied)
break;
@@ -1127,7 +1128,7 @@ int generic_ptrace_peekdata(struct task_struct *tsk, unsigned long addr,
unsigned long tmp;
int copied;

- copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
+ copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), FOLL_FORCE);
if (copied != sizeof(tmp))
return -EIO;
return put_user(tmp, (unsigned long __user *)data);
@@ -1138,7 +1139,8 @@ int generic_ptrace_pokedata(struct task_struct *tsk, unsigned long addr,
{
int copied;

- copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
+ copied = access_process_vm(tsk, addr, &data, sizeof(data),
+ FOLL_FORCE | FOLL_WRITE);
return (copied == sizeof(data)) ? 0 : -EIO;
}

@@ -1155,7 +1157,8 @@ int compat_ptrace_request(struct task_struct *child, compat_long_t request,
switch (request) {
case PTRACE_PEEKTEXT:
case PTRACE_PEEKDATA:
- ret = access_process_vm(child, addr, &word, sizeof(word), 0);
+ ret = access_process_vm(child, addr, &word, sizeof(word),
+ FOLL_FORCE);
if (ret != sizeof(word))
ret = -EIO;
else
@@ -1164,7 +1167,8 @@ int compat_ptrace_request(struct task_struct *child, compat_long_t request,

case PTRACE_POKETEXT:
case PTRACE_POKEDATA:
- ret = access_process_vm(child, addr, &data, sizeof(data), 1);
+ ret = access_process_vm(child, addr, &data, sizeof(data),
+ FOLL_FORCE | FOLL_WRITE);
ret = (ret != sizeof(data) ? -EIO : 0);
break;

diff --git a/mm/memory.c b/mm/memory.c
index bac2d99..e18c57b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3951,20 +3951,16 @@ int access_remote_vm(struct mm_struct *mm, unsigned long addr,
* Do not walk the page table directly, use get_user_pages
*/
int access_process_vm(struct task_struct *tsk, unsigned long addr,
- void *buf, int len, int write)
+ void *buf, int len, unsigned int gup_flags)
{
struct mm_struct *mm;
int ret;
- unsigned int flags = FOLL_FORCE;

mm = get_task_mm(tsk);
if (!mm)
return 0;

- if (write)
- flags |= FOLL_WRITE;
-
- ret = __access_remote_vm(tsk, mm, addr, buf, len, flags);
+ ret = __access_remote_vm(tsk, mm, addr, buf, len, gup_flags);

mmput(mm);

diff --git a/mm/nommu.c b/mm/nommu.c
index 93d5bb5..db5fd17 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1861,7 +1861,8 @@ int access_remote_vm(struct mm_struct *mm, unsigned long addr,
* Access another process' address space.
* - source/target buffer must be kernel space
*/
-int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
+int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len,
+ unsigned int gup_flags)
{
struct mm_struct *mm;

@@ -1872,8 +1873,7 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, in
if (!mm)
return 0;

- len = __access_remote_vm(tsk, mm, addr, buf, len,
- write ? FOLL_WRITE : 0);
+ len = __access_remote_vm(tsk, mm, addr, buf, len, gup_flags);

mmput(mm);
return len;
diff --git a/mm/util.c b/mm/util.c
index 4c685bd..952cbe7 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -624,7 +624,7 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
if (len > buflen)
len = buflen;

- res = access_process_vm(task, arg_start, buffer, len, 0);
+ res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);

/*
* If the nul at the end of args has been overwritten, then
@@ -639,7 +639,8 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
if (len > buflen - res)
len = buflen - res;
res += access_process_vm(task, env_start,
- buffer+res, len, 0);
+ buffer+res, len,
+ FOLL_FORCE);
res = strnlen(buffer, res);
}
}
--
2.10.0