[dpdk-dev] [PATCH] eal: fix crash on mmap error in rte_eal_hugepage_attach()

[maciej.czekaj at caviumnetworks.com]

From: Maciej Czekaj <maciej.czekaj at caviumnetworks.com>

In ASLR-enabled system, it is possible that selected
virtual space is occupied by program segments. Therefore,
error path should not blindly unmap all memmory segments
but only those already mapped.

Steps that lead to crash:
1. memeseg 0 in secondary process overlaps
   with libc.so
2. mmap of /dev/zero fails for virtual space of memseg 0
3. munmap of memseg 0 leads to unmapping libc.so itself
4. app gets SIGSEGV after returning from syscall to libc

Fixes: ea329d7f8e34 ("mem: fix leak after mapping failure")

Signed-off-by: Maciej Czekaj <maciej.czekaj at caviumnetworks.com>
---
 lib/librte_eal/linuxapp/eal/eal_memory.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c b/lib/librte_eal/linuxapp/eal/eal_memory.c
index 612626c..1dfe223 100644
--- a/lib/librte_eal/linuxapp/eal/eal_memory.c
+++ b/lib/librte_eal/linuxapp/eal/eal_memory.c
@@ -1545,6 +1545,7 @@ rte_eal_hugepage_attach(void)
 	struct hugepage_file *hp = NULL;
 	unsigned num_hp = 0;
 	unsigned i, s = 0; /* s used to track the segment number */
+	unsigned max_seg = RTE_MAX_MEMSEG;
 	off_t size;
 	int fd, fd_zero = -1, fd_hugepage = -1;
 
@@ -1603,6 +1604,9 @@ rte_eal_hugepage_attach(void)
 				"in /dev/zero to requested address [%p]: '%s'\n",
 				(unsigned long long)mcfg->memseg[s].len,
 				mcfg->memseg[s].addr, strerror(errno));
+			max_seg = s;
+			if (base_addr != MAP_FAILED)
+				munmap(base_addr, mcfg->memseg[s].len);
 			if (aslr_enabled() > 0) {
 				RTE_LOG(ERR, EAL, "It is recommended to "
 					"disable ASLR in the kernel "
@@ -1675,11 +1679,8 @@ rte_eal_hugepage_attach(void)
 	return 0;
 
 error:
-	s = 0;
-	while (s < RTE_MAX_MEMSEG && mcfg->memseg[s].len > 0) {
-		munmap(mcfg->memseg[s].addr, mcfg->memseg[s].len);
-		s++;
-	}
+	for (i = 0; i < max_seg && mcfg->memseg[i].len > 0; i++)
+		munmap(mcfg->memseg[i].addr, mcfg->memseg[i].len);
 	if (hp != NULL && hp != MAP_FAILED)
 		munmap(hp, size);
 	if (fd_zero >= 0)
-- 
2.7.4