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authorRichard Henderson <richard.henderson@linaro.org>2020-05-19 11:56:44 -0700
committerLaurent Vivier <laurent@vivier.eu>2020-08-23 16:57:58 +0200
commit9dba3ca5af80a7d4b5269685ceaa27ca04199cf4 (patch)
treef1206d93700dbd5bdafe8d6125341e98b024eb29
parent664441ea0111ef4dc68510d87b89b983ef838500 (diff)
downloadqemu-arm-9dba3ca5af80a7d4b5269685ceaa27ca04199cf4.tar.gz
linux-user: Validate mmap/mprotect prot value
The kernel will return -EINVAL for bits set in the prot argument that are unknown or invalid. Previously we were simply cropping out the bits that we care about. Introduce validate_prot_to_pageflags to perform this check in a single place between the two syscalls. Differentiate between the target and host versions of prot. Compute the qemu internal page_flags value at the same time. Signed-off-by: Richard Henderson <richard.henderson@linaro.org> Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Message-Id: <20200519185645.3915-2-richard.henderson@linaro.org> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
-rw-r--r--linux-user/mmap.c106
1 files changed, 73 insertions, 33 deletions
diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index 0019447892..46c7eeba9b 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -59,64 +59,96 @@ void mmap_fork_end(int child)
pthread_mutex_unlock(&mmap_mutex);
}
+/*
+ * Validate target prot bitmask.
+ * Return the prot bitmask for the host in *HOST_PROT.
+ * Return 0 if the target prot bitmask is invalid, otherwise
+ * the internal qemu page_flags (which will include PAGE_VALID).
+ */
+static int validate_prot_to_pageflags(int *host_prot, int prot)
+{
+ int valid = PROT_READ | PROT_WRITE | PROT_EXEC | TARGET_PROT_SEM;
+ int page_flags = (prot & PAGE_BITS) | PAGE_VALID;
+
+ /*
+ * For the host, we need not pass anything except read/write/exec.
+ * While PROT_SEM is allowed by all hosts, it is also ignored, so
+ * don't bother transforming guest bit to host bit. Any other
+ * target-specific prot bits will not be understood by the host
+ * and will need to be encoded into page_flags for qemu emulation.
+ */
+ *host_prot = prot & (PROT_READ | PROT_WRITE | PROT_EXEC);
+
+ return prot & ~valid ? 0 : page_flags;
+}
+
/* NOTE: all the constants are the HOST ones, but addresses are target. */
-int target_mprotect(abi_ulong start, abi_ulong len, int prot)
+int target_mprotect(abi_ulong start, abi_ulong len, int target_prot)
{
abi_ulong end, host_start, host_end, addr;
- int prot1, ret;
+ int prot1, ret, page_flags, host_prot;
- trace_target_mprotect(start, len, prot);
+ trace_target_mprotect(start, len, target_prot);
- if ((start & ~TARGET_PAGE_MASK) != 0)
+ if ((start & ~TARGET_PAGE_MASK) != 0) {
return -TARGET_EINVAL;
+ }
+ page_flags = validate_prot_to_pageflags(&host_prot, target_prot);
+ if (!page_flags) {
+ return -TARGET_EINVAL;
+ }
len = TARGET_PAGE_ALIGN(len);
end = start + len;
if (!guest_range_valid(start, len)) {
return -TARGET_ENOMEM;
}
- prot &= PROT_READ | PROT_WRITE | PROT_EXEC;
- if (len == 0)
+ if (len == 0) {
return 0;
+ }
mmap_lock();
host_start = start & qemu_host_page_mask;
host_end = HOST_PAGE_ALIGN(end);
if (start > host_start) {
/* handle host page containing start */
- prot1 = prot;
- for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
+ prot1 = host_prot;
+ for (addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(addr);
}
if (host_end == host_start + qemu_host_page_size) {
- for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
+ for (addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(addr);
}
end = host_end;
}
- ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS);
- if (ret != 0)
+ ret = mprotect(g2h(host_start), qemu_host_page_size,
+ prot1 & PAGE_BITS);
+ if (ret != 0) {
goto error;
+ }
host_start += qemu_host_page_size;
}
if (end < host_end) {
- prot1 = prot;
- for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
+ prot1 = host_prot;
+ for (addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(addr);
}
- ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size,
- prot1 & PAGE_BITS);
- if (ret != 0)
+ ret = mprotect(g2h(host_end - qemu_host_page_size),
+ qemu_host_page_size, prot1 & PAGE_BITS);
+ if (ret != 0) {
goto error;
+ }
host_end -= qemu_host_page_size;
}
/* handle the pages in the middle */
if (host_start < host_end) {
- ret = mprotect(g2h(host_start), host_end - host_start, prot);
- if (ret != 0)
+ ret = mprotect(g2h(host_start), host_end - host_start, host_prot);
+ if (ret != 0) {
goto error;
+ }
}
- page_set_flags(start, start + len, prot | PAGE_VALID);
+ page_set_flags(start, start + len, page_flags);
mmap_unlock();
return 0;
error:
@@ -360,19 +392,26 @@ abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size, abi_ulong align)
}
/* NOTE: all the constants are the HOST ones */
-abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
+abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
int flags, int fd, abi_ulong offset)
{
abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
+ int page_flags, host_prot;
mmap_lock();
- trace_target_mmap(start, len, prot, flags, fd, offset);
+ trace_target_mmap(start, len, target_prot, flags, fd, offset);
if (!len) {
errno = EINVAL;
goto fail;
}
+ page_flags = validate_prot_to_pageflags(&host_prot, target_prot);
+ if (!page_flags) {
+ errno = EINVAL;
+ goto fail;
+ }
+
/* Also check for overflows... */
len = TARGET_PAGE_ALIGN(len);
if (!len) {
@@ -438,14 +477,15 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
/* Note: we prefer to control the mapping address. It is
especially important if qemu_host_page_size >
qemu_real_host_page_size */
- p = mmap(g2h(start), host_len, prot,
+ p = mmap(g2h(start), host_len, host_prot,
flags | MAP_FIXED | MAP_ANONYMOUS, -1, 0);
- if (p == MAP_FAILED)
+ if (p == MAP_FAILED) {
goto fail;
+ }
/* update start so that it points to the file position at 'offset' */
host_start = (unsigned long)p;
if (!(flags & MAP_ANONYMOUS)) {
- p = mmap(g2h(start), len, prot,
+ p = mmap(g2h(start), len, host_prot,
flags | MAP_FIXED, fd, host_offset);
if (p == MAP_FAILED) {
munmap(g2h(start), host_len);
@@ -479,19 +519,19 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
/* msync() won't work here, so we return an error if write is
possible while it is a shared mapping */
if ((flags & MAP_TYPE) == MAP_SHARED &&
- (prot & PROT_WRITE)) {
+ (host_prot & PROT_WRITE)) {
errno = EINVAL;
goto fail;
}
- retaddr = target_mmap(start, len, prot | PROT_WRITE,
+ retaddr = target_mmap(start, len, target_prot | PROT_WRITE,
MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
-1, 0);
if (retaddr == -1)
goto fail;
if (pread(fd, g2h(start), len, offset) == -1)
goto fail;
- if (!(prot & PROT_WRITE)) {
- ret = target_mprotect(start, len, prot);
+ if (!(host_prot & PROT_WRITE)) {
+ ret = target_mprotect(start, len, target_prot);
assert(ret == 0);
}
goto the_end;
@@ -502,13 +542,13 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
if (real_end == real_start + qemu_host_page_size) {
/* one single host page */
ret = mmap_frag(real_start, start, end,
- prot, flags, fd, offset);
+ host_prot, flags, fd, offset);
if (ret == -1)
goto fail;
goto the_end1;
}
ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
- prot, flags, fd, offset);
+ host_prot, flags, fd, offset);
if (ret == -1)
goto fail;
real_start += qemu_host_page_size;
@@ -517,7 +557,7 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
if (end < real_end) {
ret = mmap_frag(real_end - qemu_host_page_size,
real_end - qemu_host_page_size, end,
- prot, flags, fd,
+ host_prot, flags, fd,
offset + real_end - qemu_host_page_size - start);
if (ret == -1)
goto fail;
@@ -533,13 +573,13 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
else
offset1 = offset + real_start - start;
p = mmap(g2h(real_start), real_end - real_start,
- prot, flags, fd, offset1);
+ host_prot, flags, fd, offset1);
if (p == MAP_FAILED)
goto fail;
}
}
the_end1:
- page_set_flags(start, start + len, prot | PAGE_VALID);
+ page_set_flags(start, start + len, page_flags);
the_end:
trace_target_mmap_complete(start);
if (qemu_loglevel_mask(CPU_LOG_PAGE)) {