From 800df627e2eabaf4a921d342a1d5162c843b7fc2 Mon Sep 17 00:00:00 2001 From: Vivek Goyal Date: Fri, 29 Aug 2014 15:18:29 -0700 Subject: resource: fix the case of null pointer access MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Richard and Daniel reported that UML is broken due to changes to resource traversal functions. Problem is that iomem_resource.child can be null and new code does not consider that possibility. Old code used a for loop and that loop will not even execute if p was null. Revert back to for() loop logic and bail out if p is null. I also moved sibling_only check out of resource_lock. There is no reason to keep it inside the lock. Following is backtrace of the UML crash. RIP: 0033:[<0000000060039b9f>] RSP: 0000000081459da0 EFLAGS: 00010202 RAX: 0000000000000000 RBX: 00000000219b3fff RCX: 000000006010d1d9 RDX: 0000000000000001 RSI: 00000000602dfb94 RDI: 0000000081459df8 RBP: 0000000081459de0 R08: 00000000601b59f4 R09: ffffffff0000ff00 R10: ffffffff0000ff00 R11: 0000000081459e88 R12: 0000000081459df8 R13: 00000000219b3fff R14: 00000000602dfb94 R15: 0000000000000000 Kernel panic - not syncing: Segfault with no mm CPU: 0 PID: 1 Comm: swapper Not tainted 3.16.0-10454-g58d08e3 #13 Stack: 00000000 000080d0 81459df0 219b3fff 81459e70 6010d1d9 ffffffff 6033e010 81459e50 6003a269 81459e30 00000000 Call Trace: [<6010d1d9>] ? kclist_add_private+0x0/0xe7 [<6003a269>] walk_system_ram_range+0x61/0xb7 [<6000e859>] ? proc_kcore_init+0x0/0xf1 [<6010d574>] kcore_update_ram+0x4c/0x168 [<6010d72e>] ? kclist_add+0x0/0x2e [<6000e943>] proc_kcore_init+0xea/0xf1 [<6000e859>] ? proc_kcore_init+0x0/0xf1 [<6000e859>] ? proc_kcore_init+0x0/0xf1 [<600189f0>] do_one_initcall+0x13c/0x204 [<6004ca46>] ? parse_args+0x1df/0x2e0 [<6004c82d>] ? parameq+0x0/0x3a [<601b5990>] ? strcpy+0x0/0x18 [<60001e1a>] kernel_init_freeable+0x240/0x31e [<6026f1c0>] kernel_init+0x12/0x148 [<60019fad>] new_thread_handler+0x81/0xa3 Fixes 8c86e70acead629aacb4a ("resource: provide new functions to walk through resources"). Reported-by: Daniel Walter Tested-by: Richard Weinberger Tested-by: Toralf Förster Tested-by: Daniel Walter Signed-off-by: Vivek Goyal Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/resource.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) (limited to 'kernel') diff --git a/kernel/resource.c b/kernel/resource.c index da14b8d09296..60c5a3856ab7 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -351,15 +351,12 @@ static int find_next_iomem_res(struct resource *res, char *name, end = res->end; BUG_ON(start >= end); - read_lock(&resource_lock); - - if (first_level_children_only) { - p = iomem_resource.child; + if (first_level_children_only) sibling_only = true; - } else - p = &iomem_resource; - while ((p = next_resource(p, sibling_only))) { + read_lock(&resource_lock); + + for (p = iomem_resource.child; p; p = next_resource(p, sibling_only)) { if (p->flags != res->flags) continue; if (name && strcmp(p->name, name)) -- cgit v1.2.3 From 74ca317c26a3f8543203b61d262c0ab2e30c384e Mon Sep 17 00:00:00 2001 From: Vivek Goyal Date: Fri, 29 Aug 2014 15:18:46 -0700 Subject: kexec: create a new config option CONFIG_KEXEC_FILE for new syscall Currently new system call kexec_file_load() and all the associated code compiles if CONFIG_KEXEC=y. But new syscall also compiles purgatory code which currently uses gcc option -mcmodel=large. This option seems to be available only gcc 4.4 onwards. Hiding new functionality behind a new config option will not break existing users of old gcc. Those who wish to enable new functionality will require new gcc. Having said that, I am trying to figure out how can I move away from using -mcmodel=large but that can take a while. I think there are other advantages of introducing this new config option. As this option will be enabled only on x86_64, other arches don't have to compile generic kexec code which will never be used. This new code selects CRYPTO=y and CRYPTO_SHA256=y. And all other arches had to do this for CONFIG_KEXEC. Now with introduction of new config option, we can remove crypto dependency from other arches. Now CONFIG_KEXEC_FILE is available only on x86_64. So whereever I had CONFIG_X86_64 defined, I got rid of that. For CONFIG_KEXEC_FILE, instead of doing select CRYPTO=y, I changed it to "depends on CRYPTO=y". This should be safer as "select" is not recursive. Signed-off-by: Vivek Goyal Cc: Eric Biederman Cc: H. Peter Anvin Tested-by: Shaun Ruffell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/kexec.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'kernel') diff --git a/kernel/kexec.c b/kernel/kexec.c index 0b49a0a58102..2bee072268d9 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -64,7 +64,9 @@ bool kexec_in_progress = false; char __weak kexec_purgatory[0]; size_t __weak kexec_purgatory_size = 0; +#ifdef CONFIG_KEXEC_FILE static int kexec_calculate_store_digests(struct kimage *image); +#endif /* Location of the reserved area for the crash kernel */ struct resource crashk_res = { @@ -341,6 +343,7 @@ out_free_image: return ret; } +#ifdef CONFIG_KEXEC_FILE static int copy_file_from_fd(int fd, void **buf, unsigned long *buf_len) { struct fd f = fdget(fd); @@ -612,6 +615,9 @@ out_free_image: kfree(image); return ret; } +#else /* CONFIG_KEXEC_FILE */ +static inline void kimage_file_post_load_cleanup(struct kimage *image) { } +#endif /* CONFIG_KEXEC_FILE */ static int kimage_is_destination_range(struct kimage *image, unsigned long start, @@ -1375,6 +1381,7 @@ COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry, } #endif +#ifdef CONFIG_KEXEC_FILE SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd, unsigned long, cmdline_len, const char __user *, cmdline_ptr, unsigned long, flags) @@ -1451,6 +1458,8 @@ out: return ret; } +#endif /* CONFIG_KEXEC_FILE */ + void crash_kexec(struct pt_regs *regs) { /* Take the kexec_mutex here to prevent sys_kexec_load @@ -2006,6 +2015,7 @@ static int __init crash_save_vmcoreinfo_init(void) subsys_initcall(crash_save_vmcoreinfo_init); +#ifdef CONFIG_KEXEC_FILE static int __kexec_add_segment(struct kimage *image, char *buf, unsigned long bufsz, unsigned long mem, unsigned long memsz) @@ -2682,6 +2692,7 @@ int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name, return 0; } +#endif /* CONFIG_KEXEC_FILE */ /* * Move into place and start executing a preloaded standalone -- cgit v1.2.3