sys-apps/sandbox: fix crashes when the system is prelinked #599894

2 files changed, 108 insertions, 0 deletions

diff --git a/sys-apps/sandbox/files/sandbox-2.11-exec-prelink.patch b/sys-apps/sandbox/files/sandbox-2.11-exec-prelink.patch
new file mode 100644
index 000000000000..067824f7e703
--- /dev/null
+++ b/sys-apps/sandbox/files/sandbox-2.11-exec-prelink.patch
@@ -0,0 +1,107 @@
+From 5628d830548e91819953d2d14397170e219df7c6 Mon Sep 17 00:00:00 2001
+From: Mike Frysinger <vapier@gentoo.org>
+Date: Wed, 16 Nov 2016 15:59:28 -0500
+Subject: [PATCH] libsandbox: fix symtab walking with prelinked ELFs
+
+When prelink runs on an ELF, it moves the string table from right
+after the symbol table to the end, and then replaces the string
+table with its liblist table.  This ends up breaking sandbox's
+assumption that the string table always follows the symbol table
+leading to prelinked ELFs crashing.
+
+Update the range check to use the liblist table when available.
+Since the prelink code has this logic hardcoded (swapping the
+string table for the liblist table), this should be OK for now.
+
+URL: https://bugs.gentoo.org/599894
+Reported-by: Anders Larsson <anders.gentoo@larsson.xyz>
+Reported-by: Kenton Groombridge <rustyvega@comcast.net>
+Reported-by: Marien Zwart <marien.zwart@gmail.com>
+Signed-off-by: Mike Frysinger <vapier@gentoo.org>
+---
+ libsandbox/wrapper-funcs/__wrapper_exec.c | 39 ++++++++++++++++++++++---------
+ 1 file changed, 28 insertions(+), 11 deletions(-)
+
+diff --git a/libsandbox/wrapper-funcs/__wrapper_exec.c b/libsandbox/wrapper-funcs/__wrapper_exec.c
+index d372366c5478..226c0c0f4407 100644
+--- a/libsandbox/wrapper-funcs/__wrapper_exec.c
++++ b/libsandbox/wrapper-funcs/__wrapper_exec.c
+@@ -83,8 +83,8 @@ static bool sb_check_exec(const char *filename, char *const argv[])
+ ({ \
+ 	Elf##n##_Ehdr *ehdr = (void *)elf; \
+ 	Elf##n##_Phdr *phdr = (void *)(elf + ehdr->e_phoff); \
+-	Elf##n##_Addr vaddr, filesz, vsym = 0, vstr = 0, vhash = 0; \
+-	Elf##n##_Off offset, symoff = 0, stroff = 0, hashoff = 0; \
++	Elf##n##_Addr vaddr, filesz, vsym = 0, vstr = 0, vhash = 0, vliblist = 0; \
++	Elf##n##_Off offset, symoff = 0, stroff = 0, hashoff = 0, liblistoff = 0; \
+ 	Elf##n##_Dyn *dyn; \
+ 	Elf##n##_Sym *sym, *symend; \
+ 	uint##n##_t ent_size = 0, str_size = 0; \
+@@ -102,11 +102,12 @@ static bool sb_check_exec(const char *filename, char *const argv[])
+ 			dyn = (void *)(elf + phdr[i].p_offset); \
+ 			while (dyn->d_tag != DT_NULL) { \
+ 				switch (dyn->d_tag) { \
+-				case DT_SYMTAB: vsym = dyn->d_un.d_val; break; \
+-				case DT_SYMENT: ent_size = dyn->d_un.d_val; break; \
+-				case DT_STRTAB: vstr = dyn->d_un.d_val; break; \
+-				case DT_STRSZ:  str_size = dyn->d_un.d_val; break; \
+-				case DT_HASH:   vhash = dyn->d_un.d_val; break; \
++				case DT_SYMTAB:      vsym = dyn->d_un.d_val; break; \
++				case DT_SYMENT:      ent_size = dyn->d_un.d_val; break; \
++				case DT_STRTAB:      vstr = dyn->d_un.d_val; break; \
++				case DT_STRSZ:       str_size = dyn->d_un.d_val; break; \
++				case DT_HASH:        vhash = dyn->d_un.d_val; break; \
++				case DT_GNU_LIBLIST: vliblist = dyn->d_un.d_val; break; \
+ 				} \
+ 				++dyn; \
+ 			} \
+@@ -126,6 +127,8 @@ static bool sb_check_exec(const char *filename, char *const argv[])
+ 				stroff = offset + (vstr - vaddr); \
+ 			if (vhash >= vaddr && vhash < vaddr + filesz) \
+ 				hashoff = offset + (vhash - vaddr); \
++			if (vliblist >= vaddr && vliblist < vaddr + filesz) \
++				liblistoff = offset + (vliblist - vaddr); \
+ 		} \
+ 		\
+ 		/* Finally walk the symbol table.  This should generally be fast as \
+@@ -133,19 +136,33 @@ static bool sb_check_exec(const char *filename, char *const argv[])
+ 		 * out there do not export any symbols at all. \
+ 		 */ \
+ 		if (symoff && stroff) { \
+-			/* Hash entries are always 32-bits. */ \
+-			uint32_t *hashes = (void *)(elf + hashoff); \
+ 			/* Nowhere is the # of symbols recorded, or the size of the symbol \
+ 			 * table.  Instead, we do what glibc does: use the sysv hash table \
+ 			 * if it exists, else assume that the string table always directly \
+ 			 * follows the symbol table.  This seems like a poor assumption to \
+-			 * make, but glibc has gotten by this long. \
++			 * make, but glibc has gotten by this long.  See determine_info in \
++			 * glibc's elf/dl-addr.c. \
++			 * \
++			 * Turns out prelink will violate that assumption.  Fortunately it \
++			 * will insert its liblist at the same location all the time -- it \
++			 * replaces the string table with its liblist table. \
++			 * \
++			 * Long term, we should behave the same as glibc and walk the gnu \
++			 * hash table first before falling back to the raw symbol table. \
+ 			 * \
+ 			 * We don't sanity check the ranges here as you aren't executing \
+ 			 * corrupt programs in the sandbox. \
+ 			 */ \
+ 			sym = (void *)(elf + symoff); \
+-			symend = vhash ? (sym + hashes[1]) : (void *)(elf + stroff); \
++			if (vhash) { \
++				/* Hash entries are always 32-bits. */ \
++				uint32_t *hashes = (void *)(elf + hashoff); \
++				symend = sym + hashes[1]; \
++			} else if (vliblist) \
++				symend = (void *)(elf + liblistoff); \
++			else \
++				symend = (void *)(elf + stroff); \
++			\
+ 			while (sym < symend) { \
+ 				char *symname = (void *)(elf + stroff + sym->st_name); \
+ 				if (ELF##n##_ST_VISIBILITY(sym->st_other) == STV_DEFAULT && \
+-- 
+2.10.2
+
diff --git a/sys-apps/sandbox/sandbox-2.11-r2.ebuild b/sys-apps/sandbox/sandbox-2.11-r3.ebuild
index 1319c3770ed8..e49dd8c5a1a9 100644
--- a/sys-apps/sandbox/sandbox-2.11-r2.ebuild
+++ b/sys-apps/sandbox/sandbox-2.11-r3.ebuild
@@ -34,6 +34,7 @@ sandbox_death_notice() {
 src_prepare() {
 	epatch "${FILESDIR}"/${P}-execvpe.patch #578516
 	epatch "${FILESDIR}"/${P}-exec-hash.patch #578524
+	epatch "${FILESDIR}"/${P}-exec-prelink.patch #599894
 	epatch_user
 }