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proc/linux: Don't open mmapped files before checking stat results #2002

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merged 1 commit into from
Nov 7, 2023
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proc/linux: Don't open mmapped files before checking stat results #2002

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30 changes: 19 additions & 11 deletions libyara/proc/linux.c
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Original file line number Diff line number Diff line change
Expand Up @@ -161,19 +161,13 @@ YR_API const uint8_t* yr_process_fetch_memory_block_data(YR_MEMORY_BLOCK* block)

// Only try mapping the file if it has a path and belongs to a device
if (strlen(proc_info->map_path) > 0 &&
!(proc_info->map_dmaj == 0 && (proc_info->map_dmin == 0 || proc_info->map_dmin == 5)))
!(proc_info->map_dmaj == 0 && proc_info->map_dmin == 0))
{
struct stat st;
fd = open(proc_info->map_path, O_RDONLY);

if (fd < 0)
{
fd = -1; // File does not exist.
}
else if (fstat(fd, &st) < 0)
if (stat(proc_info->map_path, &st) < 0)
{
// Why should stat fail after file open? Treat like missing.
close(fd);
fd = -1;
}
else if (
Expand All @@ -182,22 +176,36 @@ YR_API const uint8_t* yr_process_fetch_memory_block_data(YR_MEMORY_BLOCK* block)
(st.st_ino != proc_info->map_ino))
{
// Wrong file, may have been replaced. Treat like missing.
close(fd);
fd = -1;
}
else if (st.st_size < proc_info->map_offset + block->size)
{
// Mapping extends past end of file. Treat like missing.
close(fd);
fd = -1;
}
else if ((st.st_mode & S_IFMT) != S_IFREG)
{
// Correct filesystem object, but not a regular file. Treat like
// uninitialized mapping.
close(fd);
fd = -2;
}
else
{
fd = open(proc_info->map_path, O_RDONLY);
// Double-check against race conditions
struct stat st2;
if (fstat(fd, &st2) < 0)
{
close(fd);
fd = -1;
}
else if ((st.st_dev != st2.st_dev) || (st.st_ino != st2.st_ino))
{
// File has been changed from under us, so ignore.
close(fd);
fd = -1;
}
}
}

if (fd >= 0)
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