From 6a6cbe75dbdfaed6c4bbc2f109d69808f9cfa421 Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Thu, 7 Jun 2018 17:09:59 -0700 Subject: [PATCH] proc: simpler iterations for /proc/*/cmdline "rv" variable is used both as a counter of bytes transferred and an error value holder but it can be reduced solely to error values if original start of userspace buffer is stashed and used at the very end. [akpm@linux-foundation.org: simplify cleanup code] Link: http://lkml.kernel.org/r/20180221193009.GA28678@avx2 Signed-off-by: Alexey Dobriyan Reviewed-by: Andrew Morton Cc: Andy Shevchenko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/base.c | 33 ++++++++++++++------------------- 1 file changed, 14 insertions(+), 19 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 4b27e26fc6de..3fcca77d45f1 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -215,8 +215,9 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, unsigned long arg_start, arg_end, env_start, env_end; unsigned long len1, len2, len; unsigned long p; + char __user *buf0 = buf; char c; - ssize_t rv; + int rv; BUG_ON(*pos < 0); @@ -253,25 +254,20 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, len2 = env_end - env_start; /* Empty ARGV. */ - if (len1 == 0) { - rv = 0; - goto out_free_page; - } + if (len1 == 0) + goto end; + /* * Inherently racy -- command line shares address space * with code and data. */ - if (access_remote_vm(mm, arg_end - 1, &c, 1, FOLL_ANON) != 1) { - rv = 0; - goto out_free_page; - } - - rv = 0; + if (access_remote_vm(mm, arg_end - 1, &c, 1, FOLL_ANON) != 1) + goto end; if (c == '\0') { /* Command line (set of strings) occupies whole ARGV. */ if (len1 <= *pos) - goto out_free_page; + goto end; p = arg_start + *pos; len = len1 - *pos; @@ -281,7 +277,7 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, nr_read = min3(count, len, PAGE_SIZE); nr_read = access_remote_vm(mm, p, page, nr_read, FOLL_ANON); if (nr_read == 0) - goto out_free_page; + goto end; if (copy_to_user(buf, page, nr_read)) { rv = -EFAULT; @@ -292,7 +288,6 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, len -= nr_read; buf += nr_read; count -= nr_read; - rv += nr_read; } } else { /* @@ -323,7 +318,7 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, nr_read = min3(count, len, PAGE_SIZE); nr_read = access_remote_vm(mm, p, page, nr_read, FOLL_ANON); if (nr_read == 0) - goto out_free_page; + goto end; /* * Command line can be shorter than whole ARGV @@ -340,10 +335,9 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, len -= nr_write; buf += nr_write; count -= nr_write; - rv += nr_write; if (nr_write < nr_read) - goto out_free_page; + goto end; } /* Only first chunk can be read partially. */ @@ -352,12 +346,13 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, } } +end: + *pos += buf - buf0; + rv = buf - buf0; out_free_page: free_page((unsigned long)page); out_mmput: mmput(mm); - if (rv > 0) - *pos += rv; return rv; } -- 2.25.1