The patch titled
Subject: proc: simpler iterations for /proc/*/cmdline
has been added to the -mm tree. Its filename is
proc-simpler-iterations-for-proc-cmdline.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/proc-simpler-iterations-for-proc-cmdline.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/proc-simpler-iterations-for-proc-cmdline.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
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------------------------------------------------------
From: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Subject: 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.
Link: http://lkml.kernel.org/r/20180221193009.GA28678@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 36 +++++++++++++++++-------------------
1 file changed, 17 insertions(+), 19 deletions(-)
diff -puN fs/proc/base.c~proc-simpler-iterations-for-proc-cmdline fs/proc/base.c
--- a/fs/proc/base.c~proc-simpler-iterations-for-proc-cmdline
+++ a/fs/proc/base.c
@@ -238,8 +238,9 @@ static ssize_t proc_pid_cmdline_read(str
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);
@@ -269,25 +270,20 @@ static ssize_t proc_pid_cmdline_read(str
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, 0) != 1) {
- rv = 0;
- goto out_free_page;
- }
-
- rv = 0;
+ if (access_remote_vm(mm, arg_end - 1, &c, 1, 0) != 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;
@@ -297,7 +293,7 @@ static ssize_t proc_pid_cmdline_read(str
nr_read = min3(count, len, PAGE_SIZE);
nr_read = access_remote_vm(mm, p, page, nr_read, 0);
if (nr_read == 0)
- goto out_free_page;
+ goto end;
if (copy_to_user(buf, page, nr_read)) {
rv = -EFAULT;
@@ -308,7 +304,6 @@ static ssize_t proc_pid_cmdline_read(str
len -= nr_read;
buf += nr_read;
count -= nr_read;
- rv += nr_read;
}
} else {
/*
@@ -339,7 +334,7 @@ static ssize_t proc_pid_cmdline_read(str
nr_read = min3(count, len, PAGE_SIZE);
nr_read = access_remote_vm(mm, p, page, nr_read, 0);
if (nr_read == 0)
- goto out_free_page;
+ goto end;
/*
* Command line can be shorter than whole ARGV
@@ -356,10 +351,9 @@ static ssize_t proc_pid_cmdline_read(str
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. */
@@ -368,12 +362,16 @@ static ssize_t proc_pid_cmdline_read(str
}
}
+end:
+ free_page((unsigned long)page);
+ mmput(mm);
+ *pos += buf - buf0;
+ return buf - buf0;
+
out_free_page:
free_page((unsigned long)page);
out_mmput:
mmput(mm);
- if (rv > 0)
- *pos += rv;
return rv;
}
_
Patches currently in -mm which might be from adobriyan@xxxxxxxxx are
proc-revalidate-kernel-thread-inodes-to-root-root.patch
proc-fix-proc-loadavg-regression.patch
proc-make-proc-cmdline-go-through-lsm.patch
proc-more-unsigned-int-in-proc-cmdline.patch
proc-somewhat-simpler-code-for-proc-cmdline.patch
proc-simpler-iterations-for-proc-cmdline.patch
proc-deduplicate-proc-cmdline-implementation.patch
coredump-fix-spam-with-zero-vma-process.patch
seq_file-delete-small-value-optimization.patch
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