From 9e6863a537e66e01f5819dc356c5405a2bc67dc7 Mon Sep 17 00:00:00 2001 From: Joe Simmons-Talbott Date: Mon, 19 Jun 2023 10:43:34 -0400 Subject: hurd: readv: Get rid of alloca Replace alloca with a scratch_buffer to avoid potential stack overflows. Checked on i686-gnu and x86_64-linux-gnu Message-Id: <20230619144334.2902429-1-josimmon@redhat.com> --- sysdeps/posix/readv.c | 28 ++++++++++++---------------- 1 file changed, 12 insertions(+), 16 deletions(-) diff --git a/sysdeps/posix/readv.c b/sysdeps/posix/readv.c index 91208e9894..9cdf571787 100644 --- a/sysdeps/posix/readv.c +++ b/sysdeps/posix/readv.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include #include @@ -26,9 +27,9 @@ static void -ifree (char **ptrp) +ifree (struct scratch_buffer *sbuf) { - free (*ptrp); + scratch_buffer_free (sbuf); } /* Read data from file descriptor FD, and put the result in the @@ -52,20 +53,15 @@ __readv (int fd, const struct iovec *vector, int count) bytes += vector[i].iov_len; } - /* Allocate a temporary buffer to hold the data. We should normally - use alloca since it's faster and does not require synchronization - with other threads. But we cannot if the amount of memory - required is too large. */ - char *buffer; - char *malloced_buffer __attribute__ ((__cleanup__ (ifree))) = NULL; - if (__libc_use_alloca (bytes)) - buffer = (char *) __alloca (bytes); - else - { - malloced_buffer = buffer = (char *) malloc (bytes); - if (buffer == NULL) - return -1; - } + /* Allocate a temporary buffer to hold the data. Use a scratch_buffer + since it's faster for small buffer sizes but can handle larger + allocations as well. */ + + struct scratch_buffer __attribute__ ((__cleanup__ (ifree))) buf; + scratch_buffer_init (&buf); + if (!scratch_buffer_set_array_size (&buf, 1, bytes)) + return -1; + char *buffer = buf.data; /* Read the data. */ ssize_t bytes_read = __read (fd, buffer, bytes); -- cgit 1.4.1