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author | Joe Simmons-Talbott <josimmon@redhat.com> | 2023-06-21 16:00:53 -0400 |
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committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2023-06-26 10:17:39 -0300 |
commit | 48170127d984f41cd59dfc1b9ee40f729d953bf9 (patch) | |
tree | 4b2896ac6fa30a982c5e79781c6854c9ad2b2e10 | |
parent | 45e2483a6cd920b38d287c51c5363f03a34f92da (diff) | |
download | glibc-48170127d984f41cd59dfc1b9ee40f729d953bf9.tar.gz glibc-48170127d984f41cd59dfc1b9ee40f729d953bf9.tar.xz glibc-48170127d984f41cd59dfc1b9ee40f729d953bf9.zip |
ifaddrs: Get rid of alloca
Use scratch_buffer and malloc rather than alloca to avoid potential stack overflows. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
-rw-r--r-- | sysdeps/unix/sysv/linux/ifaddrs.c | 46 |
1 files changed, 20 insertions, 26 deletions
diff --git a/sysdeps/unix/sysv/linux/ifaddrs.c b/sysdeps/unix/sysv/linux/ifaddrs.c index 184ee224cb..0db9bb7847 100644 --- a/sysdeps/unix/sysv/linux/ifaddrs.c +++ b/sysdeps/unix/sysv/linux/ifaddrs.c @@ -16,13 +16,13 @@ License along with the GNU C Library; if not, see <https://www.gnu.org/licenses/>. */ -#include <alloca.h> #include <assert.h> #include <errno.h> #include <ifaddrs.h> #include <net/if.h> #include <netinet/in.h> #include <netpacket/packet.h> +#include <scratch_buffer.h> #include <stdbool.h> #include <stdint.h> #include <stdlib.h> @@ -131,26 +131,14 @@ __netlink_request (struct netlink_handle *h, int type) ssize_t read_len; bool done = false; -#ifdef PAGE_SIZE - /* Help the compiler optimize out the malloc call if PAGE_SIZE - is constant and smaller or equal to PTHREAD_STACK_MIN/4. */ - const size_t buf_size = PAGE_SIZE; -#else - const size_t buf_size = __getpagesize (); -#endif - bool use_malloc = false; - char *buf; - - if (__libc_use_alloca (buf_size)) - buf = alloca (buf_size); - else - { - buf = malloc (buf_size); - if (buf != NULL) - use_malloc = true; - else - goto out_fail; - } + /* Netlink requires that user buffer needs to be either 8kb or page size + (whichever is bigger), however this has been changed over time and now + 8Kb is sufficient (check NLMSG_DEFAULT_SIZE on Linux + linux/include/linux/netlink.h). */ + const size_t buf_size = 8192; + char *buf = malloc (buf_size); + if (buf == NULL) + goto out_fail; struct iovec iov = { buf, buf_size }; @@ -229,13 +217,11 @@ __netlink_request (struct netlink_handle *h, int type) h->end_ptr = nlm_next; } - if (use_malloc) - free (buf); + free(buf); return 0; out_fail: - if (use_malloc) - free (buf); + free(buf); return -1; } @@ -324,6 +310,8 @@ getifaddrs_internal (struct ifaddrs **ifap) char *ifa_data_ptr; /* Pointer to the unused part of memory for ifa_data. */ int result = 0; + struct scratch_buffer buf; + scratch_buffer_init (&buf); *ifap = NULL; @@ -425,7 +413,12 @@ getifaddrs_internal (struct ifaddrs **ifap) } /* Table for mapping kernel index to entry in our list. */ - map_newlink_data = alloca (newlink * sizeof (int)); + if (!scratch_buffer_set_array_size (&buf, newlink, sizeof (int))) + { + result = -1; + goto exit_free; + } + map_newlink_data = buf.data; memset (map_newlink_data, '\xff', newlink * sizeof (int)); ifa_data_ptr = (char *) &ifas[newlink + newaddr]; @@ -820,6 +813,7 @@ getifaddrs_internal (struct ifaddrs **ifap) exit_free: __netlink_free_handle (&nh); __netlink_close (&nh); + scratch_buffer_free (&buf); return result; } |