From: Vaibhav Jain vaibhav@linux.ibm.com
[ Upstream commit cbf9c4b9617b6767886a913705ca14b7600c77db ]
Presently ima_get_kexec_buffer() doesn't check if the previous kernel's ima-kexec-buffer lies outside the addressable memory range. This can result in a kernel panic if the new kernel is booted with 'mem=X' arg and the ima-kexec-buffer was allocated beyond that range by the previous kernel. The panic is usually of the form below:
$ sudo kexec --initrd initrd vmlinux --append='mem=16G'
<snip> BUG: Unable to handle kernel data access on read at 0xc000c01fff7f0000 Faulting instruction address: 0xc000000000837974 Oops: Kernel access of bad area, sig: 11 [#1] <snip> NIP [c000000000837974] ima_restore_measurement_list+0x94/0x6c0 LR [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160 Call Trace: [c00000000371fa80] [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160 [c00000000371fb00] [c0000000020512c4] ima_init+0x80/0x108 [c00000000371fb70] [c0000000020514dc] init_ima+0x4c/0x120 [c00000000371fbf0] [c000000000012240] do_one_initcall+0x60/0x2c0 [c00000000371fcc0] [c000000002004ad0] kernel_init_freeable+0x344/0x3ec [c00000000371fda0] [c0000000000128a4] kernel_init+0x34/0x1b0 [c00000000371fe10] [c00000000000ce64] ret_from_kernel_thread+0x5c/0x64 Instruction dump: f92100b8 f92100c0 90e10090 910100a0 4182050c 282a0017 3bc00000 40810330 7c0802a6 fb610198 7c9b2378 f80101d0 <a1240000> 2c090001 40820614 e9240010 ---[ end trace 0000000000000000 ]---
Fix this issue by checking returned PFN range of previous kernel's ima-kexec-buffer with page_is_ram() to ensure correct memory bounds.
Fixes: 467d27824920 ("powerpc: ima: get the kexec buffer passed by the previous kernel") Cc: Frank Rowand frowand.list@gmail.com Cc: Prakhar Srivastava prsriva@linux.microsoft.com Cc: Lakshmi Ramasubramanian nramas@linux.microsoft.com Cc: Thiago Jung Bauermann bauerman@linux.ibm.com Cc: Rob Herring robh@kernel.org Cc: Ritesh Harjani ritesh.list@gmail.com Cc: Robin Murphy robin.murphy@arm.com Signed-off-by: Vaibhav Jain vaibhav@linux.ibm.com Signed-off-by: Rob Herring robh@kernel.org Link: https://lore.kernel.org/r/20220531041446.3334259-1-vaibhav@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/of/kexec.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)
diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c index 8d374cc552be..91b04b04eec4 100644 --- a/drivers/of/kexec.c +++ b/drivers/of/kexec.c @@ -126,6 +126,7 @@ int ima_get_kexec_buffer(void **addr, size_t *size) { int ret, len; unsigned long tmp_addr; + unsigned long start_pfn, end_pfn; size_t tmp_size; const void *prop;
@@ -140,6 +141,22 @@ int ima_get_kexec_buffer(void **addr, size_t *size) if (ret) return ret;
+ /* Do some sanity on the returned size for the ima-kexec buffer */ + if (!tmp_size) + return -ENOENT; + + /* + * Calculate the PFNs for the buffer and ensure + * they are with in addressable memory. + */ + start_pfn = PHYS_PFN(tmp_addr); + end_pfn = PHYS_PFN(tmp_addr + tmp_size - 1); + if (!page_is_ram(start_pfn) || !page_is_ram(end_pfn)) { + pr_warn("IMA buffer at 0x%lx, size = 0x%zx beyond memory\n", + tmp_addr, tmp_size); + return -EINVAL; + } + *addr = __va(tmp_addr); *size = tmp_size;