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getcwd(2): saner logics around prepend_path() call

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The only negative value that might get returned by prepend_path() is
-ENAMETOOLONG, and that happens only on overflow.  The same goes for
prepend_unreachable().  Overflow is detectable by observing negative
buflen, so we can simplify the control flow around the prepend_path()
call.  Expand prepend_unreachable(), while we are at it - that's the
only caller.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2021-05-17 21:56:38 -04:00
parent 9024348f53
commit a0378fb9b3
1 changed files with 4 additions and 13 deletions
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17
fs/d_path.c
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@ -211,11 +211,6 @@ char *d_absolute_path(const struct path *path,
return res;
}
static int prepend_unreachable(char **buffer, int *buflen)
{
return prepend(buffer, buflen, "(unreachable)", 13);
}
static void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
{
unsigned seq;
@ -414,17 +409,13 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
int buflen = PATH_MAX;
prepend(&cwd, &buflen, "", 1);
error = prepend_path(&pwd, &root, &cwd, &buflen);
if (prepend_path(&pwd, &root, &cwd, &buflen) > 0)
prepend(&cwd, &buflen, "(unreachable)", 13);
rcu_read_unlock();
if (error < 0)
if (buflen < 0) {
error = -ENAMETOOLONG;
goto out;
/* Unreachable from current root */
if (error > 0) {
error = prepend_unreachable(&cwd, &buflen);
if (error)
goto out;
}
error = -ERANGE;