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authorLinus Torvalds <torvalds@linux-foundation.org>2019-07-13 13:40:13 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-07-16 09:57:52 -0700
commit3d712546d8ba9f25cdf080d79f90482aa4231ed4 (patch)
treed391efbe325a7ec74c2766a7cb3e04d555f674c5 /fs/proc/base.c
parent0ecfebd2b52404ae0c54a878c872bb93363ada36 (diff)
downloadlinux-3d712546d8ba9f25cdf080d79f90482aa4231ed4.tar.bz2
/proc/<pid>/cmdline: remove all the special cases
Start off with a clean slate that only reads exactly from arg_start to arg_end, without any oddities. This simplifies the code and in the process removes the case that caused us to potentially leak an uninitialized byte from the temporary kernel buffer. Note that in order to start from scratch with an understandable base, this simplifies things _too_ much, and removes all the legacy logic to handle setproctitle() having changed the argument strings. We'll add back those special cases very differently in the next commit. Link: https://lore.kernel.org/lkml/20190712160913.17727-1-izbyshev@ispras.ru/ Fixes: f5b65348fd77 ("proc: fix missing final NUL in get_mm_cmdline() rewrite") Cc: Alexey Izbyshev <izbyshev@ispras.ru> Cc: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/proc/base.c')
-rw-r--r--fs/proc/base.c71
1 files changed, 8 insertions, 63 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 255f6754c70d..8040f9d1cf07 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -212,7 +212,7 @@ static int proc_root_link(struct dentry *dentry, struct path *path)
static ssize_t get_mm_cmdline(struct mm_struct *mm, char __user *buf,
size_t count, loff_t *ppos)
{
- unsigned long arg_start, arg_end, env_start, env_end;
+ unsigned long arg_start, arg_end;
unsigned long pos, len;
char *page;
@@ -223,36 +223,18 @@ static ssize_t get_mm_cmdline(struct mm_struct *mm, char __user *buf,
spin_lock(&mm->arg_lock);
arg_start = mm->arg_start;
arg_end = mm->arg_end;
- env_start = mm->env_start;
- env_end = mm->env_end;
spin_unlock(&mm->arg_lock);
if (arg_start >= arg_end)
return 0;
- /*
- * We have traditionally allowed the user to re-write
- * the argument strings and overflow the end result
- * into the environment section. But only do that if
- * the environment area is contiguous to the arguments.
- */
- if (env_start != arg_end || env_start >= env_end)
- env_start = env_end = arg_end;
-
- /* .. and limit it to a maximum of one page of slop */
- if (env_end >= arg_end + PAGE_SIZE)
- env_end = arg_end + PAGE_SIZE - 1;
-
/* We're not going to care if "*ppos" has high bits set */
- pos = arg_start + *ppos;
-
/* .. but we do check the result is in the proper range */
- if (pos < arg_start || pos >= env_end)
+ pos = arg_start + *ppos;
+ if (pos < arg_start || pos >= arg_end)
return 0;
-
- /* .. and we never go past env_end */
- if (env_end - pos < count)
- count = env_end - pos;
+ if (count > arg_end - pos)
+ count = arg_end - pos;
page = (char *)__get_free_page(GFP_KERNEL);
if (!page)
@@ -262,48 +244,11 @@ static ssize_t get_mm_cmdline(struct mm_struct *mm, char __user *buf,
while (count) {
int got;
size_t size = min_t(size_t, PAGE_SIZE, count);
- long offset;
- /*
- * Are we already starting past the official end?
- * We always include the last byte that is *supposed*
- * to be NUL
- */
- offset = (pos >= arg_end) ? pos - arg_end + 1 : 0;
-
- got = access_remote_vm(mm, pos - offset, page, size + offset, FOLL_ANON);
- if (got <= offset)
+ got = access_remote_vm(mm, pos, page, size, FOLL_ANON);
+ if (got <= 0)
break;
- got -= offset;
-
- /* Don't walk past a NUL character once you hit arg_end */
- if (pos + got >= arg_end) {
- int n = 0;
-
- /*
- * If we started before 'arg_end' but ended up
- * at or after it, we start the NUL character
- * check at arg_end-1 (where we expect the normal
- * EOF to be).
- *
- * NOTE! This is smaller than 'got', because
- * pos + got >= arg_end
- */
- if (pos < arg_end)
- n = arg_end - pos - 1;
-
- /* Cut off at first NUL after 'n' */
- got = n + strnlen(page+n, offset+got-n);
- if (got < offset)
- break;
- got -= offset;
-
- /* Include the NUL if it existed */
- if (got < size)
- got++;
- }
-
- got -= copy_to_user(buf, page+offset, got);
+ got -= copy_to_user(buf, page, got);
if (unlikely(!got)) {
if (!len)
len = -EFAULT;