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Date: Fri, 27 Nov 2020 13:20:29 +0000
From: Szabolcs Nagy <szabolcs.nagy@....com>
To: libc-alpha@...rceware.org
Cc: Mark Rutland <mark.rutland@....com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
linux-kernel@...r.kernel.org,
Jeremy Linton <jeremy.linton@....com>,
Mark Brown <broonie@...nel.org>,
kernel-hardening@...ts.openwall.com,
Topi Miettinen <toiwoton@...il.com>,
linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v2 3/6] elf: Fix failure handling in _dl_map_object_from_fd
There are many failure paths that call lose to do local cleanups
in _dl_map_object_from_fd, but it did not clean everything.
Handle l_phdr, l_libname and mapped segments in the common failure
handling code.
There are various bits that may not be cleaned properly on failure
(e.g. executable stack, tlsid, incomplete dl_map_segments).
---
elf/dl-load.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 21e55deb19..9c71b7562c 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -914,8 +914,15 @@ lose (int code, int fd, const char *name, char *realname, struct link_map *l,
/* The file might already be closed. */
if (fd != -1)
(void) __close_nocancel (fd);
+ if (l != NULL && l->l_map_start != 0)
+ _dl_unmap_segments (l);
if (l != NULL && l->l_origin != (char *) -1l)
free ((char *) l->l_origin);
+ if (l != NULL && !l->l_libname->dont_free)
+ free (l->l_libname);
+ if (l != NULL && l->l_phdr_allocated)
+ free ((void *) l->l_phdr);
+
free (l);
free (realname);
@@ -1256,7 +1263,11 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
errstring = _dl_map_segments (l, fd, header, type, loadcmds, nloadcmds,
maplength, has_holes, loader);
if (__glibc_unlikely (errstring != NULL))
- goto call_lose;
+ {
+ /* Mappings can be in an inconsistent state: avoid unmap. */
+ l->l_map_start = l->l_map_end = 0;
+ goto call_lose;
+ }
/* Process program headers again after load segments are mapped in
case processing requires accessing those segments. Scan program
@@ -1294,14 +1305,6 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
|| (__glibc_unlikely (l->l_flags_1 & DF_1_PIE)
&& __glibc_unlikely ((mode & __RTLD_OPENEXEC) == 0)))
{
- /* We are not supposed to load this object. Free all resources. */
- _dl_unmap_segments (l);
-
- if (!l->l_libname->dont_free)
- free (l->l_libname);
-
- if (l->l_phdr_allocated)
- free ((void *) l->l_phdr);
if (l->l_flags_1 & DF_1_PIE)
errstring
@@ -1392,6 +1395,9 @@ cannot enable executable stack as shared object requires");
/* Signal that we closed the file. */
fd = -1;
+ /* Failures before this point are handled locally via lose.
+ No more failures are allowed in this function until return. */
+
/* If this is ET_EXEC, we should have loaded it as lt_executable. */
assert (type != ET_EXEC || l->l_type == lt_executable);
--
2.17.1
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