From 47005e8d4c9aeda5826c17c4a013cfbda1a3f2de Mon Sep 17 00:00:00 2001 From: Georgy Yakovlev Date: Mon, 12 Oct 2020 14:29:17 -0700 Subject: [PATCH] opal-prd: handle devtmpfs mounted with noexec On systems using recent versions of systemd /dev (devtmpfs) is mounted with noexec option. Such mount prevents mapping HBRT image code region as RWX from /dev. This commit, as suggested in github PR linked below, attempts to work around the situation by copying HBRT image to anon mmaped memory region and sets mprotect rwx on it, allowing opal-prd to sucessfully execute the code region. Having memory region set as RWX is not ideal for security, but fixing that is a separate and hard to solve problem. Original code also mmaped region as RWX, so this PR does not make things worse at least. Closes: https://github.com/open-power/skiboot/issues/258 Signed-off-by: Georgy Yakovlev Reviewed-by: Vasant Hegde [oliver: whitespace fix, add a comment, reflow commit message] Signed-off-by: Oliver O'Halloran --- external/opal-prd/opal-prd.c | 36 ++++++++++++++++++++++++++++++++++-- 1 file changed, 34 insertions(+), 2 deletions(-) diff --git a/external/opal-prd/opal-prd.c b/external/opal-prd/opal-prd.c index d74d80398d..12269e8ebb 100644 --- a/external/opal-prd/opal-prd.c +++ b/external/opal-prd/opal-prd.c @@ -973,7 +973,9 @@ static int map_hbrt_file(struct opal_prd_ctx *ctx, const char *name) static int map_hbrt_physmem(struct opal_prd_ctx *ctx, const char *name) { struct prd_range *range; + int rc; void *buf; + void *ro_buf; range = find_range(name, 0); if (!range) { @@ -981,15 +983,45 @@ static int map_hbrt_physmem(struct opal_prd_ctx *ctx, const char *name) return -1; } - buf = mmap(NULL, range->size, PROT_READ | PROT_WRITE | PROT_EXEC, + ro_buf = mmap(NULL, range->size, PROT_READ, MAP_PRIVATE, ctx->fd, range->physaddr); - if (buf == MAP_FAILED) { + if (ro_buf == MAP_FAILED) { pr_log(LOG_ERR, "IMAGE: mmap(range:%s, " "phys:0x%016lx, size:0x%016lx) failed: %m", name, range->physaddr, range->size); return -1; } + buf = mmap(NULL, range->size, PROT_READ | PROT_WRITE, + MAP_SHARED | MAP_ANONYMOUS, -1 , 0); + if (buf == MAP_FAILED) { + pr_log(LOG_ERR, "IMAGE: anon mmap(size:0x%016lx) failed: %m", + range->size); + return -1; + } + + memcpy(buf, ro_buf, range->size); + + rc = munmap(ro_buf, range->size); + if (rc < 0) { + pr_log(LOG_ERR, "IMAGE: munmap(" + "phys:0x%016lx, size:0x%016lx) failed: %m", + range->physaddr, range->size); + return -1; + } + + /* + * FIXME: We shouldn't be mapping the memory as RWX, but HBRT appears to + * require the ability to write into the image at runtime. + */ + rc = mprotect(buf, range->size, PROT_READ | PROT_WRITE | PROT_EXEC); + if (rc < 0) { + pr_log(LOG_ERR, "IMAGE: mprotect(phys:%p, " + "size:0x%016lx, rwx) failed: %m", + buf, range->size); + return -1; + } + ctx->code_addr = buf; ctx->code_size = range->size; return 0;