[ktap] [PATCH] symbol: fix segmentation fault at sdt_note_addr()
- From: Azat Khuzhin <a3at.mail@xxxxxxxxx>
- To: ktap@xxxxxxxxxxxxx
- Date: Thu, 14 Nov 2013 00:08:08 +0400
Because dst.d_buf must be 24 bytes long (on x86-64) while there is only
8 bytes (allocated on stack).
return address was at: 0x7fffffffdd88
dst.d_buf: 0x7fffffffdd78
And after elf64_xlatetom() executed, it called memmove() into dst.d_buf,
and overwrite return address for sdt_note_addr(), and after retq
executed it jumps to 0x0.
Signed-off-by: Azat Khuzhin <a3at.mail@xxxxxxxxx>
---
userspace/symbol.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/userspace/symbol.c b/userspace/symbol.c
index f3d5fc6..789611e 100644
--- a/userspace/symbol.c
+++ b/userspace/symbol.c
@@ -172,11 +172,20 @@ static vaddr_t sdt_note_addr(Elf *elf, const char *data,
size_t len, int type)
vaddr_t vaddr;
/*
+ * Three addresses need to be obtained :
+ * Marker location, address of base section and semaphore location
+ */
+ union {
+ Elf64_Addr a64[3];
+ Elf32_Addr a32[3];
+ } buf;
+
+ /*
* dst and src are required for translation from file to memory
* representation
*/
Elf_Data dst = {
- .d_buf = &vaddr, .d_type = ELF_T_ADDR, .d_version = EV_CURRENT,
+ .d_buf = &buf, .d_type = ELF_T_ADDR, .d_version = EV_CURRENT,
.d_size = gelf_fsize(elf, ELF_T_ADDR, SDT_NOTE_COUNT,
EV_CURRENT),
.d_off = 0, .d_align = 0
};
@@ -199,6 +208,8 @@ static vaddr_t sdt_note_addr(Elf *elf, const char *data,
size_t len, int type)
elf_getident(elf, NULL)[EI_DATA]) == NULL)
return 0; /* TODO */
+ memcpy(&vaddr, &buf, sizeof(vaddr));
+
return vaddr;
}
--
1.8.4.rc3
Other related posts:
- » [ktap] [PATCH] symbol: fix segmentation fault at sdt_note_addr() - Azat Khuzhin
