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fdcheck: update fdcheck impl
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1 store fd in the high position
2 removing the pid information , as the tag information is sufficient.

Signed-off-by: hujun5 <hujun5@xiaomi.com>
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@hujun260
hujun260 committed Apr 10, 2024
1 parent 729e9fc commit 9fb7b03
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Showing 3 changed files with 40 additions and 107 deletions.
28 changes: 13 additions & 15 deletions include/nuttx/fdcheck.h
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Original file line number Diff line number Diff line change
Expand Up @@ -46,49 +46,47 @@ extern "C"
*
* Description: Obtain original fd information
*
* Val carries the pid, tag and fd information.
* The original fd information is stored in low bit of val.
* The pid and tag information is stored in the high bit of val.
* Val carries the tag and fd information.
* The original fd information is stored in high bit of val.
* The tag information is stored in the low bit of val.
* For ease of understanding, let's give an example where
* the following information is represented in 32-bit binary format
*
* val 00000000 01010101 00000001 10001010
* val 00000000 00000000 10001010 00000001
* fd 00000000 00000000 00000000 10001010
* pid 00000000 00000000 00000000 01010101
* tag 00000000 00000000 00000000 00000001
*
* In this function, we also check if the pid and tag information is correct.
* In this function, we also check tag information is correct.
* If there is an error, it will panic.
*
* Input Parameters:
* val - this val carrying pid, tag and original fd information
* val - this val carrying tag and original fd information
*
* Returned Value: none
* Returned Value: The original fd is returned.
*
****************************************************************************/

int fdcheck_restore(int fd);
int fdcheck_restore(int val);

/****************************************************************************
* Name: fdcheck_protect
*
* Description: Obtain the combined value of fd, pid and tag
* Description: Obtain the combined value of fd and tag
*
* the return value carries the pid, tag and fd information.
* the return value carries the tag and fd information.
* The original fd information is stored in low bit of val.
* The pid and tag information is stored in high bit of val.
* The tag information is stored in high bit of val.
* For ease of understanding, let's give an example where
* the following information is represented in 32-bit binary format
*
* fd 00000000 00000000 00000000 10001010
* pid 00000000 00000000 00000000 01010101
* tag 00000000 00000000 00000000 00000001
* val 00000000 01010101 00000001 10001010
* val 00000000 00000000 10001010 00000001
*
* Input Parameters:
* fd - original fd
*
* Returned Value: the combined value of fd and pid
* Returned Value: the combined value of fd and tag
*
****************************************************************************/

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107 changes: 21 additions & 86 deletions libs/libc/misc/lib_fdcheck.c
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Original file line number Diff line number Diff line change
Expand Up @@ -37,17 +37,15 @@
* Pre-processor Definitions
****************************************************************************/

#define FD_SHIFT 0
#define FD_BITS LOG2_CEIL(OPEN_MAX)
#define FD_MASK ((1 << FD_BITS) - 1)

#define TAG_SHIFT (FD_BITS + FD_SHIFT)
#define TAG_SHIFT 0
#define TAG_BITS 8
#define TAG_MASK ((1 << TAG_BITS) - 1)

#define PID_SHIFT (TAG_BITS + TAG_SHIFT)
#define PID_BITS (8 * sizeof(int) - 1 - PID_SHIFT)
#define PID_MASK ((1 << PID_BITS) - 1)
#define FD_SHIFT (TAG_SHIFT + TAG_BITS)
#define FD_BITS LOG2_CEIL(OPEN_MAX)
#define FD_MASK ((1 << FD_BITS) - 1)

static_assert(FD_BITS <= TAG_BITS, "FD_BITS is too long");

/****************************************************************************
* Private Data
Expand All @@ -60,95 +58,34 @@ static uint8_t g_fdcheck_tag = 0;
* Public Functions
****************************************************************************/

/****************************************************************************
* Name: fdcheck_restore
*
* Description: Obtain original fd information
*
* Val carries the pid, tag and fd information.
* The original fd information is stored in low bit of val.
* The pid and tag information is stored in the high bit of val.
* For ease of understanding, let's give an example where
* the following information is represented in 32-bit binary format
*
* val 00000000 01010101 00000001 10001010
* fd 00000000 00000000 00000000 10001010
* pid 00000000 00000000 00000000 01010101
* tag 00000000 00000000 00000000 00000001
*
* In this function, we also check if the pid and tag information is correct.
* If there is an error, it will panic.
*
* Input Parameters:
* val - this val carrying pid, tag and original fd information
*
* Returned Value: none
*
****************************************************************************/

int fdcheck_restore(int val)
{
int pid_expect;
int ppid_now;
int pid_now;
uint8_t tag_store;
int fd;

if (val <= 2)
{
return val;
}
/* If val is a bare fd（0~255）, we should return it directly */

pid_expect = (val >> PID_SHIFT) & PID_MASK;
pid_now = _SCHED_GETPID() & PID_MASK;
ppid_now = _SCHED_GETPPID() & PID_MASK;
if (pid_expect != pid_now && pid_expect != ppid_now && pid_expect != 0)
fd = (val >> FD_SHIFT) & FD_MASK;
if (fd == 0 || val < 0)
{
ferr("pid_expect %d pid_now %d ppid_now %d\n",
pid_expect, pid_now, ppid_now);
PANIC();
return val;
}

if (pid_expect != 0)
int ret = ioctl(fd, FIOC_GETTAG_FDCHECK, &tag_store);
if (ret >= 0)
{
uint8_t tag_store;
int ret = ioctl(val & FD_MASK, FIOC_GETTAG_FDCHECK, &tag_store);
if (ret >= 0)
uint8_t tag_expect = (val >> TAG_SHIFT) & TAG_MASK;
if (tag_expect != tag_store)
{
uint8_t tag_expect = (val >> TAG_SHIFT) & TAG_MASK;
if (tag_expect != tag_store)
{
ferr("tag_expect 0x%x tag_store 0x%x\n",
tag_expect, tag_store);
PANIC();
}
ferr("tag_expect 0x%x tag_store 0x%x\n",
tag_expect, tag_store);
PANIC();
}
}

return val & FD_MASK;
return fd;
}

/****************************************************************************
* Name: fdcheck_protect
*
* Description: Obtain the combined value of fd, pid and tag
*
* the return value carries the pid, tag and fd information.
* The original fd information is stored in low bit of val.
* The pid and tag information is stored in high bit of val.
* For ease of understanding, let's give an example where
* the following information is represented in 32-bit binary format
*
* fd 00000000 00000000 00000000 10001010
* pid 00000000 00000000 00000000 01010101
* tag 00000000 00000000 00000000 00000001
* val 00000000 01010101 00000001 10001010
*
* Input Parameters:
* fd - original fd
*
* Returned Value: the combined value of fd and pid
*
****************************************************************************/

int fdcheck_protect(int fd)
{
int protect_fd;
Expand All @@ -160,9 +97,7 @@ int fdcheck_protect(int fd)
return fd;
}

protect_fd = fd & FD_MASK;
protect_fd |= (_SCHED_GETPID() & PID_MASK) << PID_SHIFT;

protect_fd = (fd & FD_MASK) << FD_SHIFT;
ret = ioctl(fd, FIOC_GETTAG_FDCHECK, &tag);
DEBUGASSERT(ret >= 0);
if (tag == 0)
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12 changes: 6 additions & 6 deletions libs/libc/stdio/lib_fopen.c
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Original file line number Diff line number Diff line change
Expand Up @@ -105,6 +105,12 @@ FAR FILE *fdopen(int fd, FAR const char *mode)
/* Initialize the mutex the manages access to the buffer */

nxrmutex_init(&filep->fs_lock);

#ifdef CONFIG_FDSAN
android_fdsan_exchange_owner_tag(fd, 0,
android_fdsan_create_owner_tag(ANDROID_FDSAN_OWNER_TYPE_FILE,
(uintptr_t)filep));
#endif
}
else
{
Expand Down Expand Up @@ -135,12 +141,6 @@ FAR FILE *fdopen(int fd, FAR const char *mode)
filep->fs_cookie = (FAR void *)(intptr_t)fd;
filep->fs_oflags = oflags;

#ifdef CONFIG_FDSAN
android_fdsan_exchange_owner_tag(fd, 0,
android_fdsan_create_owner_tag(ANDROID_FDSAN_OWNER_TYPE_FILE,
(uintptr_t)filep));
#endif

/* Assign custom callbacks to NULL. */

filep->fs_iofunc.read = NULL;
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