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linux-user: Validate mmap/mprotect prot value

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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>
This commit is contained in:
Richard Henderson 2020-05-19 11:56:44 -07:00 committed by Laurent Vivier
parent 664441ea01
commit 9dba3ca5af
1 changed files with 73 additions and 33 deletions
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106
linux-user/mmap.c
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@ -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)) {